ISSN 1453 - 7303no.3 / October 2010

ENVIRONMENT

ECOLOGY

RENEWABLE ENERGY

Magazine of

HIDRAULICS, PNEUMATICS, TRIBOLOGY, ECOLOGY, SENZORICS, MECHATRONICS

4 3

1. Phd.Eng. Petrin DRUMEA ( Hydraulics & Pneumatics Research Institute, Bucharest – Romania) pp.5 – 62.

pp. 7 - 243.

pp. 25 – 27

4.

pp. 28 - 29

5.

pp. 30 – 356.

pp.36 – 40

7.

pp. 41 - 48

8.

pp. 49 - 56

9.

EDITORIAL

RENEWABLE ENERGIES - A HUGE GENERATOR OF BUSINESS OPPORTUNITIES

HYBRID TECHNOLOGY - Eco-solutions based on cutting-edge technologies

MORE SPEED FOR SELF-DRIVEN MOBILE MACHINERY ICVD - speeds up hydrostatically driven vehicles to 80 km/h

INVESTIGATIONS OF GAS FORMATION IN SMALL WASTEWATER TREATMENT SYSTEMS

CONTROL OF WATER TURBINE GUIDE APPARATUS BY USE OF WATER HYDRAULIC ACTUATOR

EVALUATION OF THE ELASTOMER HYPER ELASTIC BEHAVIOR A U-CUP HYDRAULIC ROD SEAL

EXPERIMENTAL IDENTIFICATION OF ELECTROHYDRAULIC SERVOMECHANISMS WITH VIRTUAL INSTRUMENTS TECHNIQUE

RECIRCULATION OF POWER AT ENDURANCE AND RELIABILITY STANDS

ISSUES RELATING TO THE METHODOLOGY OF ESTABLISHING THE WATER IRRIGATION NEEDS

NATURAL VENTILATION INDUCED BY SOLAR AIR COLLECTORS

RENEWABLE ENERGY TECHNOLOGIES VS. CLIMATE CHANGE

ELEVATION AND TRANSPORT EQUIPMENT WITH DOUBLE SOURCE OF ENERGY

OPTIMISATION OF THE TARGET CONTROL WITH NEURAL NETWORK

Ph.D.Eng. Petrin DRUMEA, Eng. Cătălin DUMITRESCU, Ph.D.Eng. Dragoş-Daniel GUŢĂ - INOE 2000 – IHP Bucharest

Oswald Mutter-Head Business Area Hydraulics BIBUS AG Group

Oswald Mutter-Head Business Area Hydraulics BIBUS AG Group

Dr.-Ing. Elmar Dorgeloh, Dipl.-Ing. Patricia Khan - Prüf- und Entwicklungsinstitut für Abwassertechnik an der RWTH Aachen

PhD student Pawel WALCZAK and Dr. MS. Eng. Andrzej SOBCZYK - Cracow University of Technology

A. Fatu, M. Crudu, M. Hajjam, S. Cananau, A. Pascu -PPRIME Institute, CNRS – University of Poitiers

Ph.D.eng. Dragos Ion GUTA, Ph.D.stud.eng. Catalin DUMITRESCU, Ph.D.eng. Ioan LEPADATU, Ph.D.eng. Corneliu CRISTESCU - INOE 2000 - IHP

Ph.stud.Eng.Radu Radoi, eng.Mirela Tudor, eng.I.Balan-INOE 2000 - IHP pp. 57 - 5910.

Constantin NICOLESCU, Gheorghe ŞOVĂIALĂ-INOE 2000 - IHP pp. 60 - 6211.

Prof.Adrian CIOCANEA, Lect. Sanda BUDEA - University Politehnica Bucharest, Department of Hydraulics pp. 63 - 6912.

Conf. Dr.ing. Petre Lucian Seiciu-University Politehnica Bucharest pp.70 - 7813.

eng. Florin GEORGESCU, eng. Liliana DUMITRESCU,PhD. eng. Dragoş GUŢĂ-INOE 2000-IHP ,

eng. Laurentiu VEBER-SC PRESTCOM SA pp. 79 - 8314.

Adrian Olaru, Aurel Oprean-UPB,Bucharest,Romania,Serban Olaru- RomSYS Company, Bucharest, Romania, Dan Paune, General Manager, S.C.Metal Plast, Bucharest, Romania pp. 84 - 101

Specialized reviewers: Adrian MIREAPhD. eng. (ROMFLUID S.A. Bucharest) Math. eng. Gabriel RĂDULESCU (INOE 2000 -IHP Bucharest) Prof. PhD.eng. Guido BELFORTE (Politecnico di Torino, Italia)

Prof. PhD. eng. Pavel MACH (Czech Technical University in Prague, Czech Republic)

Editorial Board: Nicolae ALEXANDRESCUProf. PhD. eng. Nicolae VASILIUProf. PhD. eng. Paul SVASTAProf. PhD. eng. Alexandru MARINProf. PhD. eng. Daniel MARINPhD. eng.

Ana-Maria Carla POPESCU

PhD. eng. Gabriela MATACHE

Valentin MIROIU

Graphics & DTP:Valentin MIROIU

e-mail: vmiroiu.ihp@fluidas.ro

e-mail: hidraulica@fluidas.ro

e-mail: vmiroiu.ihp@fluidas.ro

Executive editors:

PhD. eng. Petrin DRUMEAPhD. eng. Corneliu CRISTESCUPhD. eng. Ion PIRNAPhD. eng. Dragos ION GUTA

No.3 / October 2010

4

1. Page format is A4 (210 x 297)2. The text of an article, drawings included, shall not exceed 8 conventional pages. 3. The article shall be draft in two columns, using MS Office Word 97 to 2010, preferably with fonts Arial CE or Times New Roman, font size 12, at 1 (one) line in page; diacritical marks shall be used. Also, formulas shall be written in Arial CE too; Microsoft Equation is recommended. 4. Since no. 1 / 2008 issue of "HIDRAULICA" articles submitted for publishing shall be written in English.5. Together with article shall be presented also an abstract of the paper in 10 rows and keywords; abstract and keywords shall be written in English.6. All figures and tables included in articles must be mentioned in text; figures and captions must have titles.7. When authors belong to several institutions, each author is marked with a number of asterisks. Each number of asterisks will be associated with an institution. Caption of asterisks will be presented at bottom of page. For the first author or corresponding author is an e-mail address shall be provided.8. Tables and figures will be presented in the following formats: .bmp, .jpeg, .tiff, .eps, .ai, .cdr;9. Papers must be original contributions of the author, not remakes or translations of other papers.10. Authors retain full responsibility for the accuracy of statements expressed, for calculations and results displayed.11. Not allowed for publishing papers that were published in full or in part in other publications. 12. Review committee reserves the right to make recommendations for improving the articles or to not publish material regarded as inappropriate. Unpublished manuscripts are not returned.13. Magazine does not grant copyrights.14. Paper intended to be published shall be submitted via one of the e-mail addresses : hidraulica@fluidas.ro or fluidas@fluidas.ro.

No.3 / October 2010

55

No.3 / October 2010

ROMANIAN HYDRAULIC POWER IN THE WORLD

We are living in a world in course of globalization, in which who does not comprehend properly the historical trend of nowadays will have to surmount huge difficulties in the daily life. Hydraulics and pneumatics are appropriately framed , according to the new trends of evolution, keeping the right pace both in what regards organizational issues and technical and scientific development. It is unmistakably apparent a regrouping of forces, the smaller specialised companies associating with the bigger ones, ending by a distinct presence of only a few, very representative brands in the field. In what regards technique, pneumatics have already made the qualitative leap up to the future, while hydraulics is still preparing for upgrading its technical and technological level.

In Romania this field is still affected by the economic crisis of the last years and by its ceaseless endeavours to integrate into the world elite of this domain. The number of the employees in the field was reducted over 15 times and production was also cut over 10 times, which led to such an intricate situation which we have not been able to overcome yet. Our chance is represented by the few active national cores from Bucharest, Cluj, Iasi, Ramnicu Valcea, Timisoara or Sibiu which by tremendous efforts have succeded to maintain Romanian hydraulics on the European map of this field.It is worth mentioning that big companies have come on the Romanian market but they have not proved any intention yet of starting any production of equipment, but only of systems and their most important activity is that of sale.

Despite all these facts and improper conditions, we have to mention the successfull association of the companies from the field in FLUIDAS, which has already joined CETOP, the European professional association and succeeded to promote and maintain good relationships with similar associations from other countries like Poland, Italy, Germany or Russia.

It is not negligible the cooperation between certain research and academic centres from our country with the most famous European centres of the like, even if the direct contacts between these have not been very significant.The most important system of connections of the Romanian scientists and professionals with those from other countries is that of direct contacts. It deserves mentioning here the meetings with the specialists from Aachen, Torino, Wroclaw, Cracow, Toulouse, Poitiers, Russe, Chisinau, Prague or Vienna who honoured with their presence the HERVEX annual international scientific reunion. But although the direct scientific contacts and meetings were numerous their concrete relevance to the national research and production is extremely low. The contacts of the last years on FP7 themes or structural funds seem to bring a slight change in what regards international cooperation in the field, with concrete results for Romanian hydraulics.

In the end we remark the tendency of rebuilding international relationships, on a new groundwork, according to the real demands of the national economy and to the common interests in technical and scientific activities of our most important foreign partners and the Romanian representative names in the field.

6

No.3 / October 2010

HIDRAULICA ROMANEASCA IN LUME

Traim intr-o lume in curs de globalizare, in care cine nu intelege mersul istoriei va avea mari probleme in viata de zi cu zi. Hidraulica si pneumatica se incadreaza destul de bine in noile tendinte, atat din punct de vedere al organizatorii cat si din punct de vedere al dezvoltarii tehnico-stiintifice. In acest sens se poate usor observa regruparea firmelor de specialitate in jurul celor mai puternice, in final ramanand doar cateva mari grupuri care sa fie reprezentative in domeniu. De asemenea se constata ca tehnic pneumatica a efectuat deja saltul calitativ spre viitor in timp ce hidraulica este inca in etapa pregatirii trecerii spre urmatorul nivel tehnic si tehnologic. In Romania domeniul inca are de suferit atat de pe urma integrarii la nivel mondial cat si de pe urma crizei economico-financiare a ultimilor ani. Reducerea numarului lucratorilor din domeniu de peste 15 ori, a fabricatiei de peste 10 ori a condus la o situatie din care inca nu reusim sa iesim. Sansa noastra o constituie existenta celor cateva nuclee active la nivel national Bucuresti, Cluj, Iasi, Ramnicu Valcea, Timisoara,Sibiu, care cu eforturi deosebite reusesc sa mentina hidraulica pe harta europeana a domeniului. Este interesant ca marile firme au patruns in Romania, dar deocamdata fara activitatea de fabricatie de echipamente ci doar de sisteme si de vanzare a echipamentelor fabricate in alte tari. Chiar si in aceste conditii s-a reusit crearea unei asociatii a firmelor cu preocupari in domeniu FLUIDAS care fost integrata la nivel european in CETOP si care a reusit sa asigure legaturi foarte bune, inclusiv la nivel de protocoale directe de cooperare cu asociatiile similare din tari ca Polonia, Italia Germania sau Rusia. Nu este de neglijat nici sistemul relational al unor centre de cercetare si academice din tara noastra cu cele mai prodigioase centre de expertiza europene, chiar daca pana acum contractele directe intre acestea nu sunt semnificative.

Cel mai important sistem de legaturi al specialistilor romani cu cei din alte tari il reprezinta cel al legaturilor directe. Dintre acestea as remarca pe cele cu specialistii din Aachen, Torino, Wroclaw, Cracovia, Toulouse, Poitiers, Russe, Chisinau, Praga si Viena care au fost si la intalnirile anuale realizate sub genericul HERVEX. Consider ca desi numarul contactelor personale este destul de mare, efectul acestora asupra cercetarii si productiei nationale este extrem de scazut. Contactele ultimilor ani pe teme de FP7 sau pe Fonduri Structurale par sa modifice ideea simplista de mobilitati si sa se treaca la cooperarea internationala in domeniu, cu rezultate concrete pentru domeniul hidraulicii romanesti. In final trebuie remarcata tendinta de reasezare a legaturilor internationale pe directia cerintelor reale ale economiei nationale si primele elemente serioase de activitati tehnico-stiintifice si de productie comune cu principalii actori internationali din domeniu.

7

No.3 / October 2010

RENEWABLE ENERGIES - A HUGE GENERATOR OF BUSINESS OPPORTUNITIES

Authors: Ph.D.Eng. Petrin DRUMEA*, Eng. Cătălin DUMITRESCU*, Ph.D.Eng. Dragoş-Daniel GUŢĂ*

* - INOE 2000 – IHP Bucharest

Abstract: Nowadays mankind is confronted with a very serious energetic crisis and has started to become interested in the primary energy sources and concerns a lot about the possible profitable uses of renewable energies. May be considered renewable kinds of energy those forms of energy coming from sources whose use does not affect by any means the natural resources for the future generations or which by their intrinsic character regenerate themselves or do not deplete during time.

Keywords: renewables, energy, research

GENERAL CONSIDERATIONS The main sources from which may be

obtained pure natural energy are:- Solar radiation- Wind energy- Wave energy- Geothermal energy - Cereals and other plants which may be

used as fuel- Biomass and its and the derived forms

The use of these kinds of energy increased in time and has become very significant lately. The main reasons which led to a greater concern towards solar energy depend on the actual. economic, social and geographic conjuncture:

- The natural resources of fossil fuels are scarce and their prices are continously rising. Most of the gases used for producing thermal enrgy in our country are imported, this having a negative impact upon the economic balance

- The production of thermal and electric energy by traditional means, which uses mainly the combustion of fossil fuels damages the environment, becoming more and more restricted

RENEWABLE ENERGIES WHICH CAN BE USED IN ROMANIA

1. WIND ENERGY

1.1. General considerat ions regarding wind energy

Wind energy represents that form of energy which is mostly increasing. Europe is the continent which produces most of the energy using wind power. For 2010 World Wide Energy Association presumes to be produced on global scale 160 GW of electricity using wind energy.

The economic success of the wind turbines of 500 – 1000 kW is conditioned by their location in zones with powerful and constand winds. A new trend is that which shows interest in low power turbines of less than 100 kW integrated in decentralized systems delivered,

No.3 / October 2010

purposefully used mainly in the rural zones with less powerful winds, like those from our country. Comparing with the large wind turbines, the low power turbines are more versatile and have a higher potential of technological development. The beneficiaries of this system are the rural communities, the installations which operate in isolated zones and especially small energetic consumers from zones with potential in using wind energy.

1.2. Equipment for conversionTurbines with horizontal axis- The helix is proximate the turbine centroid, increasing stability- The alignment of the helix with the wind direction offers the best angle of operation for it, maximizing the resulted electric energy- The helix blades allow acces to more powerful winds, resulting a higher current produced by the turbine

Turbines with vertical axis- Their maintenance is much easier- Have a high aerodynamic efficiency at high and low pressures- For the same dyameter of the helix the blades of a turbine have a larger section than the turbines with horizontal axis- Are more efficient in the zones with wind turbulence- The top of the turbine blades have a lower angular speed therefore withstand more powerful winds than the turbines with horizontal axis

1.3. The making of an aeolian parkFor making it, should be taken into

account the following aspects:- Must be found the location depending on the size of the projected park. Then will be performed wind power measurements in that location. After finishing them it is necessary to analyze carefully the data acquired, for setting the proper operational conditions for the turbines, for finding an optimum balance between delivery, costs and production acquired.- Must be obtained the licenses and authorisations necessary for implementing the project- Build the roads which facilitate the access to it and the networks connecting the Aeolian park to The National Energetic System, build the conversion station and the foudations- Install turbines test them and put them into operation- The investor must sign a contract for the energy produced, a service and maintenance agreement and obtain the licence of producer

The value of the investment and the period of amortization

The overall costs for an Aeolian park vary between 1,3 and 1,5 mil.euro installed MW. The cost on installed MW may vary depending on the project features and the chosen technical solutions

The costs of an Aeolian system for household use

For the jouses which are not connected to the national network of electric energy, the price for an Aeolian system comprising a turbine accumulators and electronic devices vary between 1.200 and 12.000 euro.

1.4. Opportunities for the companies interested in investing in the field

Romania has a relevant potential in what regards wind energy, fact which is certified by the relief, the production acquired at this moment or the interest of certain international companies in implementing large projects in the zones with high energetic potential. According to the studies performed in Valcea county, this region has a significant wind potential. The locations where can be produced green energy are Voineasa, Vidra and Obarsia Lotrului,

8

No.3 / October 2010

Malaia, Brezoi and Horezu. The optimum wind height is of 1500 m.

1.5. How INOE 2000 - IHP can support a potential investor in producing installations of this type- By designing and dimensioning the systems for orientation in the wind of the turbine nacelles- By designing and realizing the automatic revolution regulation systems- By taking part at joint research programmes for creating and validating new solutions.

2. WAVE ENERGYThe wave energy is a kind of renewable

energy with a very high potential in the zones with waves during the entire year or at sea. The wave energy implies the surface move of the waves and the underwater pressure variations. But the wave power is yet expensive and difficult .

Despite these facts the first investments in the field have already been started by companies which dream at the moment when electricity generated by the power of waves shall be exploited on industrial scale. Beside the evident advantages, the wave power have some disadvantages as well, like the visual and physical impact upon the sea life, the toxic leaks of liquids used in building the installations and the conflict with the commercial ships.

3. GEOTHERMAL ENERGYGeothermal energy is a form of energy

obtained from the heat existent inside Earth. Hot water and steam captured in the zones with volcanic and tectonic activity, are used for household heating and for producing electricity.

There are three types of geothermal plants used at this moment in the world for converting geothermal power into electricity: dry, flash and binary, depending on the status of the fluid, vapours or liquid or depending on its temperature.The advantages offered by geothermal plants are: the resulting energy is clean and safe for the environment and is also renewable, the geothermal plants are not afftected by the meteorological conditions and the night and day cycle.

The disadvantages are: the soil instability is increased in zone, even causing low intensity eartquakes. The zones with geothermal activity cool significantly after few decades of exploitation, this meaning that we cannot rely on an infinitely renewable energy source.

4. SOLAR ENERGY4.1.Generalities Factors favouring the

use of solar energy in RomaniaSolar energy is absolutely non

aggressive for the environment. Its potential beneficiaries and users is presumed to be encouraged and supported financially in the future by applying income tax cuts and granting financial aid for purchasing the installations. IN the EU there are already various kinds of financial aids and in Romania as well, have been already made the first steps in this direction (the Green House programme)

In what regards the sunlight power, Romania is in the B zone in Europe, this meaning an average of the annual solar

2radiation betweeen 1250 – 1600 kWh/m /year value which is higher than those of countries with a powerful solar industry like: Germany which has an annual solar radiation of 876-

21250 kWh/m /year.

9

No.3 / October 2010

Other values from Europe are inferior or equal with that from our country: Liege - 840, Hamburg - 870, Munchen – 950, Madrid - 1400, Sevilla - 1470.

The geographical location combined with the climatic changes caused by the greenhouse effect generate 210 sunny days per year, which leads to a high sunpower value level.

Figure 4.1.1 - Average solar energy on the territory of Romania

A more detailed picture particularized for the Southern zone of our country which benefit from the most auspicious conditions for exploiting this type of energy may be found in the table from below.

2Table 1 - Annual average solar energy kW /m /day in some towns from the South of Romania

10

No.3 / October 2010

4.2. Equipment for conversionThe equipment for converting solar

radiation into other forms of energy are the solar panels created in two variants: photovoltaic or thermal.

Figure 4.1.2. - Photovoltaic solar panels

Figure 4.1.3 - Thermal solar panels integrated in the structure of a house

Solar panels occupy a small space and may be integrated in the existent structure of the houses.

A photovoltaic solar panel converts solar energy directly into electric energy. The main components of the solar panel are the solar cells. The solar panels are used separatedly or connected in batterries for supplying individual consumers or for generating electric current which is delivered in the public network. A solar panel is characterized by its electric parameters such is the idle voltage or shortcircuit current

This kind of solar panels are used mainly in the yones where are no other sources of electricity or for punctual uses, as a mobile form of energy. Lately the efficiency of the solar panels increased and their prices decreased, determining an increasing use for saving energy.

The main factors which impede the expansion of the photovoltaic panels are the low output of the conversion cells and the price of the equipment for storing electric energy.

The thermal so lar panels are installations which capture solar radiation and converti t into thermal energy. Their efficiency is very high ranging from 60 up to 80% relating it to the energy contained in the incidental solar beams.

There are 2 kinds of thermal panels:- Plane panels with a plain and

accessible structure with a high efficiency and which are mostly recommended to be used during the warm season from April to September They have an affordable price 100 /

2200 euro /m and may be produced by a company of average capability.

- Panels with vacuum tubes which are made by a more sophisticated technology and have a higher price but also offer a more performant work and the option to be used in the cold season as well

Figure 4.1.4 - Solar system with panel with vacuum tubes Figure 4.1.5 - Solar system made

with a plane panel

11

No.3 / October 2010

The plane solar panel may be easily produced in an average enterprise manufacturing metallic structures

The structure of a plane solar panel the plainest and most accessible is as it is shown in figure 4.1.6. the following :

1. Upper frame2. Tightproof fitting3. Special glass4. Absorbtion plate5. Winding from Cu or Al6. Lateral thermal insulation7. Bottom thermal insulation8. Bottom plate of the panel

Figure 4.1.6. - The structure of a plane solar panel

In figure 4.1.7. is shown a detail – a section of such a thermal panel and the connecting element – threaded joint.

Figure 4.1.7. - Structure of a plane solar panel detailed

1. Upper frame2. Tightproof fitting3. Bottom insulation4. Bottom plate5. Special glass

6. Cu or Al pipe7. Absorbtion plate8. Thermal insulation9. Lateral panel10.Joint

12

No.3 / October 2010

The most usual application for the systems with solar panels is for heating household water. The plainest solar system for producing hot water uses the thermosyphon principle and comprises the storage device the collector, pipes, valves, framework support and transfer fluid.

Solar collectors are fixed below the hot water storage basin. Beside the solar collector it is necessary a reservoir where is made the exchange of heat, in fact a double walled cylinder connected with the cold water inlet and the consumer.

Figure 4.1.8. - Installation for producing household hot water on the base of the

thermosyphon principle

A solution which ofers superior performance is represented by the use of thermal solar panels in combination with a pumping unit, comprising the hydraulic systems necessary for a proper work of the installation. In this case is used a reservoir with double winding bivalent boiler, where takes place the heating of the cold water. The system includes an electropump for the forced circulation of the fluid from the circuit, controlled by a solar controller on the base of the difference of temperature between the fluid from the solar panel and that from the boiler.

Figure 4.1.9 - Installation for producing hot water with pump and additional source

Beside the advantage of a higher performance, the system may be connected to a classic installation for heating water, saving energy all the year round.

An installation which produces thermal energy may be used for household heating in combination with a conventional source of thermal energy – thermal plant using various fuels, especiaally during the cold season

For all these kinds of applications exist extensively developed schemes which may represent the groundwork for the installations.

4 .3 . Techn ica l and economic characteristics of the installations with thermal solar panels

2- 1 m of solar panel provides the entire necessary of water for a person during the warm season and 20-40% during the cold season

- For a family with 3 4 members is necessary an installation with 2 solar panels each one having a surface of about 2 sm and a boiler with a capacity equal to the expected consumption for a day about 200 l

- The exploiting and maintenance costs are minimum after 3 or 4 years must be replaced just the heat bearer fluid

- The storage of the thermal energy is made easily by means of solar boilers

The solar panels can be easily installed and may be connected to conventional heating systems.

13

No.3 / October 2010

The amortization of the investment is made in 2-5 years.

The lifespan is of 20-25 years.At this moment on the market are found

all components and materials necessary for putting into operation such an installation

Besides producing hot water, the solar panels may be also used in other systems requiring thermal energy even if the temperature is lower: swimming pools and floor heating installations

The prices for the main components of such an installation are:1. Solar panel 200…400 euro / piece2. Reservoir with double winding 200…l

500 euro3. Cont ro l and management un i t

comprising solar controller, hydraulic safety elements, directional valves, solar expansion container, safety valve - 300-500 euro

4. Heat bearer liquid 1 euro/lFor an installation intended to produce

hot water for a family with 3-4 members the overall price is of about 2000 euro.

The savings which might be obtained by using a sm of thermal solar panel are significant both financially and ecologically, by reducing toxic gases generated during fuel combustion. All these are shown below.

Figure 4.1.10 - Equivalent of fuel saved by using one sm of thermal solar panel

4.5. Opportunities for the companies interested in investing in the field of thermal installations using solar energy

For a company interested in starting business in this field the opportunities of action are:– the production of components for installations: thermal solar panels, hydraulic units (in Romania there are no manufacturers of components or entire assemblies)- production of the whole systems with components manufactured by itself or imported- sale to the final beneficiaries and the assembling components, including here the operations supported financially by the governmental authorities ex.: for the Green House (Casa Verde) programme- deliver thermal energy obtained from solar energy for various users

4.6. How INOE 2000 IHP can support a potential investor in manufacturing installations of this type

- by making available for them the operational schemes of the installations- by projecting and dimensioning installations- by documentation of execution for component parts thermal solar panels hydraulic units- by taking part at partnership for developing joint research programmes, for realizing and validating the new solutions.

5. ENERGY FROM BIOMASS5.1. The use of biomass for obtaining

renewable energy, the potential of our country in the field

Biomass represents a major potential in the field of renewable energy source, being considered a relatively clean fuel which reduces CO . It has a low sulphurous content and the 2

value of the nitrogen and emission of particles is lower than at fossil fuels.

Biomass may be used for obtaining a combustible gas, used for domestic needs, for heating protected areas like greenhouses for combustion in special thermal motors adapted to this kind of fuel, for obtaining heat after making pellets and briquettes.

14

No.3 / October 2010

Biomass represents the biodegradable fraction of the products, wastes and residues from agriculture, inclusively vegetal and animal substances, forestry and the industries related to it fig.6.1.1. and the biodegradable fraction of the city wastes (industrial and domestic)

Biomass stores solar energy which may be converted by man into electricity, fuel or heat. The need for a susteinable development of the energetic field and for a proper protection of the environment led to an intensification of the preoccupations related to the promotion of the renewable energy sources and technologies. It is pursued to reach a min of 12% with the use of primary energetic sources producing electricity of at least 23,5%.

Figure 5.1.1 - Biomass sources

The overall energetic potential of the forest and agricultural biomass. In what regards the energetic potential, the territory of Romania was divided into 7 regions: Dobrogea, Moldova, Carpathians (Orientali, Meridionali and Apuseni), Transilvanian Plateau, The western plain, Subcarpatii and the southern plain.

The biomass potential of Romania

Romania has an energetic potential of biomass estimated at about 7594 thousands tep/year 9318 x 10 MJ/year representing about 19% from the total sources of primary energetic sources,

from the following categories of fuel:

15

No.3 / October 2010

The characteristics of the wastes produced in agriculture

The biomass from agriculture is more consistent than that from forests. At this source of energy may be adapted various processes like cogeneration, fermentation for producing the energy necessary for human consumption. The high potential of the biomass may be increased even more by a better use of the existent resources and by increasing productivity of crops.

Productivity of certain crops

5.2. Energetic agricultural cropsThe energetic agricultural crops are

crops planted for obtaining products like : biofuels biologic fuels, ecologic biodiesel and electric and thermal energy

The plants which are recommended for such crops are rape sunflower soya maize. IN the EU the use of energetic rops for obtaining biofuels became current. In countries like Germany, Austria France biodiesel is used for supplying tractors and agricultural machines and there are many gas stations for this.

The main trend is to use the entire amount of fuels coming from bioenergetic crops.

Biodiesel is a fuel which has identical properties to conventional diesel.

Biodiesel is a fuel which has identical properties to conventional diesel. The processing of the raw material is made in the oil refineries or enterprises manufacturing edible oil. In our country such enterprises are located in the southern yone. Biodiesel is obtained through an easy method, comparable with that through which is obtained beer. The wastes which remain unused may be used in soap industry pharmaceutical or cosmetic industry.

16

No.3 / October 2010

Since 2006 Romanian and foreign investors expressed their interest in this field : PETROM, ROMPETROL, LUKOIL.The promotion of energetic cultures and the use of biofuels offer the following advantages :- It is reducted pollution with toxic gases- The energetic crops provide safe ecologic fuels- Because the oil resources are decreasingprogressively was required an alternative forproducing fuel for tractors and agriculturalmachines- The rape oil gives the best biofuel.- An advantage of cultivating rape is thatexpenses on ha are lower than for wheat orbarley- The financial aid granted for supportingenergetic crops is of :50,55 euro/ha funds for eligible land from EUfinacing31,5 euro/ha national budgetary funds oneligible land surfaceDirect funding from MADR 400 lei/year for rapeTechnical dataProduction 4000 kg/haFor obtaining 1 l of biodiesel are necessary, 2,5

kg rapeSale price for rape 0,7 lei/kg

For obtaining profitable production at this crop it is necessary to be known and applied a proper technology.5.3. Installations which use gasification ofwooden biomass

The gasification of wooden biomass is a thermo chemical process of transforming wooden biomass into combustion fuels and the ash is eliminated during the energetic cycle.A. Heating installation with gasogen of theprotected areas is characterized by the use of atechnology which transforms into gas thebiomass, filters and cools the obtained gas andproduces its combustion in a burner for heatinggreenhouses

Component parts: - The installation comprises the following elements - see fig. 6.3.1.- Gasificator- Gas filter- Gasogen flow unit- Blower- Burner- Support frame- Flexible tubing

Operation. The gasification processes may be regarded as conversions through combustion at which is consumed less oxygen than at combustion. Depending on the relation betweeen the amount of oxygen which takes part in the reaction and that required for a complete combustion, named equivalent relation, may be calculated the composition of the obtained gas. Gasification takes place at relations ranging from 0,2 to 0,4 in the case of the relation with 0,4 taking place the max transfer of energy from the biomass to the gas. As a result of the thermo chemical gasification process of conversion it is obtained a gas of average quality. This gas contains CO, CO , H , CH and small amounts 2 2 4

of hydrocarbon, water, nitrogen and various polluters oils and tars.

Figure 5.3.1 - Heating installation with gasogen of the protected areas

17

No.3 / October 2010

B. Experimental installation made by INOE 2000 - IHP for obtaining the gas used as fuel for thermal motors

The operational scheme of the experimental installation created by INOE 2000 - IHP in collaboration with CCSB from UPB is shown in figure 6.3.2.

The gas generator comprises a metallic vat coated with refractory material where are tucked in vegetal scraps from the top which are burnt in the presence of air pumped by the blower from the central part. The ash is evacuated from the bottom. The gas passes through the cyclone, where is washed and are removed solid insoluble particles, these being pushed out htrough the bottom of the cyclone. The obtained gas (hot gas) is cooled through a drying method, in a cooler, and by water cooling. Are removed the soluble tars and the cooling water, obtaining cold gas with water vapours. This is mixed with air through the filter 7 and dried in the filter 8, being transformed into fuel gas. At starting the thermal motor 11 for which is used as fuel, it can be mixed with a fraction of conventional fuel passing through the electrovalve 10 from the reservoir 9.

The thermal motor 11 set into action the spinning pump 12 which delivers the water necessary for the irrigation installations.

Figure 5.3.2. - The scheme of the installation which produces the gasogen gas used as fuel in thermal motors

18

No.3 / October 2010

5.4. The energy obtained from granular wood scrap after compacting it

General considerationsAccording to the Agency for preserving

energy ARCE, Romania should encourage companies and citizens for investing in alternative sources of energy, so that the electric energy obtained fron renewable energy resources to reach 33% till 2013. A source of renewable energy is the biomass, and one kind of it is represented by wood scraps.

Wood scrapsAccording to FAO specialists, the wood

consumption known at the moment an increase in the developed countries, the UE directive stating that the alternative energy obtained on its base to cover about 20% from the overall necessary of energy until 2013. This shall not be made exclusively by burning raw wood; due to the fact that nowadays is a greater concern for the environment and its protection. Therefore the deforestations should be made carefully taking into account to be less than the regeneration of trees. The environment is affected by the sawdust resulted from deforestations or stored in improper conditions where it can be watered by rain and may damage phreatic water if the sawdust is in the proximity of riverbeds.

The energetic potential of wooden biomass sources

The overall surface of Romania covered with forests is of 6,22 mil.ha from which about 67% in the mountains. The total amount of wood from the Romanian forests is of 1,6 bil.

3M . The exploitable potential is of 20.000 – 3 322.000 x 10 m

The scraps resulting from cutting trees consist of branches with a breadth of less than 3 cm and roots. Until now in Romania the technologies for reusing these branches and roots were not put into practice. The wooden fuel comes from the wood resulting from cutting tree crowns which are not used in industry.

The quantities of wood scrap resulting from the industrial wood processing – sawdust, shavings, chips, are significant and most of these are used for manufacturing wooden panels or in the paper industry.

The small scraps should be compacted in the form of pellets or briquettes and used as fuel but until now in Romania has not been used this method on wide scale, just experimentally.

Equipment for converting granular wood scraps

The regulations from the UE legislation referring at the ecologic field, recommend the integral use of the wooden scraps and the acquirement of performant compacting equipments by the companies involved in the field.

A high standard technological line for capitalizing sawdust should comprise two modules:

- Module for preparing sawdust- Module for compacting sawdust

Figure 5.4.1 - The scheme of the installation for briquetting sawdust

19

No.3 / October 2010

In the technological line sawdust is stored in ermetically shut storehouses like that from below.

Figure 5.4.2 – Storehouse for wet sawdust

But very often sawdust is transported to the storehouses after it had stayed in the open air for a long time under rains and snow. It is already wet in a percentage of about 65%. For compacting it, it should be dried for reaching a humidity of not more than 10-16%. For this the sawdust should be dried in a special dryer device.

Figure 5.4.3 – PRO-DRY-R 200 - dryer with rotative roller

It is also required to sort it, being separated the particles bigger than 15 mm.For performing this operation there are special installations.

Figure 5.4.4 - Sorter L 3000 E

The transport of sawdust in the different phases of its processing is made by means of screw or band carriers. These and other equipments like the hot air generator, the dryer, the filtering system for the evacuated air and the transport piping represent the technological module for preparing sawdust. In the figure from below are shown a hot air generator and a drier.

Figure 5.4.5 - Hot air generator Kalorina K2314

20

No.3 / October 2010

Figure 5.4.6 - Hot air generator with solid fuel and air shifter

Briquettes and pellets are obtained by manual pressing of the wooden material until reducing its dimensions and obtaining a higher density. For briquettes and pellets are used preferably particles of 5 up to 15 mm. The obtained products are used as solid fuels. They are ecological, with low humidity content, economic and efficient.

Figure 5.4.7 - Cylindrical briquettes

Figure 5.4.8 - Paralelipipedic briquettes

Sawdust compacting process under the form of briquettes is performed by means of hydraulic presses which generate in the sawdus t mass p ressures o f 7 -800

2daN/cm .This pressure generates a heating controlled through a water cooling system. The volume is reducing 8 to 10 times depending on

3the humidity of the sawdust used. 1 m of sawdust with a humidity of 15% has a weight of 90…100 kg and that with humidity is 40%, the weight is 141 kg. At a humidity of 55% the weight reaches about 250 kg.

The compacting of the dried sawdust is made in more stages. It is made first a rasing and then a rasing and a pressing in the pressing device. Rasing is realized by means of a device with arms placed in the sawdust supply device. The pressing device has 2 hydraulic cylinders one for prepressing and the other for final pressing. These devices are mounted above the oil reservoir of the hydraulic powered installation.

Figure 5.4.9 - Diagram presenting compacting pressure stroke

21

No.3 / October 2010

There are many foreign companies which manufacture wooden briquettes and pellets. These kinds of products started to be sold on the Romanian market as well, as the interest for the alternative fuels increased.

Figure 5.4.10 - Briquetting machine S21

Figure 5.4.11 - Briquetting presse with

cylindric bunker

The entire process starting from sorting sawdust, passing through its drying transport and compacting and ending with the supply of the device for preparing hot air, which uses for heating sawdust with a humidity of max 30% the transport of the hot air and its filtering being monitored and automatized by means of an electric control installation, which processes the data from the pressure, temperature and humidity transducers placed on the track. The sawdust briquettes may have the dimensions of O50/ O80. In processing the entire amount of sawdust 25% of this is used for preparing hot air.

T h e t e c h n i c a l a n d e c o n o m i c characteristics of the installations for processing sawdust

If we consider as extremes humidity of 65% and of 10% after being dried, an average installation producing 100 kg of briquettes per hour needs about 250 kg wet sawdust. The compacting machines in use make 50 up to 350 kg of briquettes per hour with installed powers of 5 to 35 kW

For higher productivities is used a battery o compacting machines. For a processing line with a capacity of 200 kg briquettes per hour and complete automation of all the operations is needed a power of 140 kW

INOE 2000-IHP purposefully developed scientific studies for creating an installation for producing sawdust briquettes, to be used by small companies

The studies performed with its partners from UPB, INMA, ORASD, OVM, ICCPET, USAMV Iasi and MARVIOR EXPERT were finalized by obtaining a hydraulic press for briquetting sawdust. Also, material resulted as waste from agricultural technological processes, previously fragmented, can be briquetted.

The press comprises a briquetting chamber – hydraulic cylinder which presses the material through a nozzle.

22

No.3 / October 2010

Figure 5.4.12 - Briquetting press

The material is introduced in the pressing chamber by means of the piston which takes the biomass from the supply division. The briquette is made after the piston of the hydraulic cylinder has already finished its entire pressing stroke.

Another modality for using efficiently the agricultural wastes is the maize stalks briquetting, domain in which INOE 2000 IHP has already acquired relevant research experience, after carrying on some research projects on this issue.

The technology is similar with that from compacting wooden scrap, the technological process taking place on presses which are adapted to the current purpose.

Figure 5.4.13 - Maize stalks briquettes obtained on the sawdust presses modified for

a different operational mode

CONCLUSIONS

An efficient use of the renewable energy resources might contribute to an improvement in what regards the safety of the electricity supply, the reduction of imports and energetic costs and in what refers to the sustainable development of the energetic field and the optimum protection of the environment.

For valuing efficiently the economic potential offered by the renewable energy resources must be adopted and implemented adequate measures and policies, taking into account the demands on the market.

Our country has significant renewable resources, with a geographic location that provides a significant amount of solar energy, wind energy, with its wooded areas and important agricultural crops or different allowing the exploitation of wood and agricultural waste. However, there are possibilities of exploitation of geothermal energy, wave, etc.. In most of these areas, INOE 2000-IHP had concerns and outcomes that currently allow them to be able to assist potential investors in renewable energy by:- putting at its disposal the operational schemes of the installations- designing and dimensioning installations- the documentation of execution for the afferent devices and machines

23

No.3 / October 2010

- involving actively in scientific partnerships for creating and validating new innovative, performant solutions according with the achievements in the field existent on global scale.

Bibliography

1. Oportunitati de transfer tehnologic inovativ, in domeniul act ionari lor h i d r o p n e u m a t i c e - D r u m e a , P. – ROMCONTROLA 2010, Bucureşti, 16 – 19 martie 20102. Thermal solar installation with high efficiency that utilizes plane solar collectors –DUMITRESCU, L., GEORGESCU, F.,

t hDUMITRESCU, C., MIREA, A., - 4 International Conference on Energy and Environement, Bucharest, 12 – 14 November 2009 3. Research studies regarding the making of maize stalks briquettes – Sava, A., Dumitrescu, C., Şovăială, Gh., Hydraulics and Pneumatics 2009, Wroclaw, 7 – 9 October 2009

24

No.3 / October 2010

HYBRID TECHNOLOGYEco-solutions based on cutting-edge technologies

Prepared by Oswald Mutter, Head Business Area Hydraulics BIBUS AG Group*

* BIBUS Technology, Allmendstrasse 26, CH-8320 FehraltorfTel.: +41 (0)44 877 50 11, Fax +49 (0)44 877 58 53info@bibus.ch, www.bibus-technology.com

* BIBUS EUROFLUID SRL, Str. Scoala de Inot, Nr. 2B, RO-550005 SibiuTel.: +40 (0)26 920 67 50, Fax: +40 (0)26 920 62 75office@bibuseurofluid.ro, www.bibuseurofluid.ro

Energy Efficiency – The challenge which will shape our futureDue to an ever increasing awareness of climate change, various activities are beeing proceeded all over the world for preservation of global environment. The industry has been sharply requested to reduce the environmental influence. It is a vital issue for all manufacturers across the world to face this challenge. In fact, we can identify tree main drivers in this process:

Global trend§ Global warming control§ Saving of energy resources§ Ozone layer protection§ Reduction of natural environmental load

Social requirement§ Energy Saving§ Waste reduction and recycle§ Air pollution control§ CO2 gas emission control

Major laws and regulations§ Montreal protocol (Revised 2007)§ Air pollution Control Act CO2 emission control

Highest possible ENERGY EFFICIENCY by Power On Demand Systems based on Variable Speed Drives – this is the technology we call HYBRID ELECTRO-HYDRAULIC SYSTEMS. By thinking of a better world we all involved in the hydraulics business want to bring our contribution in creating and further developing environmentally friendly technologies which take care about our limited energy resources and environmental protection

25

No.3 / October 2010

Furthermore, energy costs are increasingly at centre stage by consideration of the total cost of ownership over the entire life of a machine.

Energy-Saving activities by reviewing machine concepts or machining lines is indispensable to protect environment and improve productivity. Machine builder and machine user are aware of their responsibility to optimize energy efficiency and environmental care. But not at the expense of precision and power. That's where we can help with our Power on Demand Systems based on Variable Speed Drives and our engineering knowledge.

The heart of our HYBRID technology is the DAIKIN IPM motor – a built-in magnet-type synchronous motor – equipped with multi-functional software and electrical inverter controller. A rare-earth permanent magnet deeply positioned in the rotor of the IPM motor c a n g e n e r a t e m a g n e t t o r q u e (attraction/repellence between coil and permanent magnet) and reluctance torque (coil attracts iron). This electromagnetic feature generates a high torque over the complete speed range, highest efficiency & low heat generation coupled with excellent dynamic control tasks.

As well by the development of new machines or the modernisation of existing one, the vital prerequisite in both cases is to make a full study of the components and subsystems which are to work together and determine not only the pure functional parameters but also the associated life cycle costs. This can produce energy savings up to 50 percent coupled with h igher product iv i ty an lower no ise development.

Our HYBRID SystemFusion of conventional hydraulic technology and electrical technology equipped with multifunctional software

Excellent efficiencyDaikin IPM motor efficiency is much higher than that of an induction motor.

High torque at the low speed rangeDaikin IPM motor produces high torque at low speed. During general use, an inverter type may at times have limited torque at low speed range; Daikin IPM motor is free of such a problematic occurrence.

26

No.3 / October 2010

Comparisson of IPM to AC servo

Coolant Pump Coolant Unit

3.3.ElectromotorElectromotor

1. Pump1. Pump2. Bell2. Bellhousinghousing

3.3.ElectromotorElectromotor 1. Pump1. Pump2. Bell2. Bellhousinghousing

1.1.PumpPump

3.3.ElectroElectro--motormotor

2. Center block2. Center block

IPM motor&Inverter Technology

IPM motor&Inverter Technology

IPM motor &Inverter Technology

EcoRich EcoRich R Super Unit

2.2.Bell Bell housinghousing

1.1.PumpPump

3.3.ElectroElectro--motormotor3.3.ElectromotorElectromotor 1. Pump1. Pump

2. Bell2. Bellhousinghousing

BlockBlock

BIBUSBIBUSBIBUSBIBUS

2.2.Bell Bell housinghousing

1.1.PumpPump

3.3.ElectroElectro--motormotor3.3.ElectromotorElectromotor 1. Pump1. Pump

2. Bell2. Bellhousinghousing

BlockBlock

BIBUSBIBUSBIBUSBIBUS

IPM motor&

Inverter Technology

IPM motor&

Inverter Technology

IPM motor&

Inverter Technology

SR motor &

Inverter Technology

The BIBUS HYBRID products at a glance:

§Energy saving §Low noise development §Compact design §High dynamics

Features and your benefits from our HYBRID solutions:

From conception to commissioning, from daily operation to retrofitting – for us ENERGY EFFICIENCY is always in our spotlight and with this we help you and your customers to protect the environment and at the same time to safe money in the long run.

27

MORE SPEED FOR SELF-DRIVEN MOBILE MACHINERYICVD speeds up hydrostatically driven vehicles to 80 km/h

Prepared by Oswald Mutter, Head Business Area Hydraulics BIBUS AG Group*

* BIBUS Technology, Allmendstrasse 26, CH-8320 FehraltorfTel.: +41 (0)44 877 50 11, Fax +49 (0)44 877 58 53info@bibus.ch, www.bibus-technology.com

* BIBUS EUROFLUID SRL, Str. Scoala de Inot, Nr. 2B, RO-550005 SibiuTel.: +40 (0)26 920 67 50, Fax: +40 (0)26 920 62 75office@bibuseurofluid.ro, www.bibuseurofluid.ro

28

No.3 / October 2010

Sauer Bibus has set a new standard for hydrostatic drives with the development and configuration of the ICVD drive. ICVD stands for "Integrated Continuously Variable Drive", which facilitates drive speeds up to 80 km/h thanks to large-angle technology in the drive motor. Thus, the drive is an interesting alternative, both economically and technically, particularly for mobile machines that are used in the high-speed range. The ICVD drive is now standard equipment for leading construction equipment manufacturers.

The success of the special drive is based on its large-angle technology. A hydraulic motor with an adjustable range of up to 45 ° is used here. This means that you can run through the entire speed range continuously. This technology means that machines that are especially used at higher speeds can do without a manual gearbox. For the operating personnel this means a clear gain in convenience and safety, as the driver can concentrate fully on driving his machine and does not have to focus on switching operations. The drive concept scores due to its cost-effectiveness, which is based on improved efficiency in the traction drive. Fuel consumption has also been positively influenced in addition to the wear on the drive system.

The ICVD is already being used as drive technology by manufacturers of large construction and agricultural machinery. "Thus, our drive concept has also made the leap into international use", commented Ralf Schrempp, Managing Director of SAUER BIBUS GmbH, on the success of his company

with the ICVD. The technology from the Neu-Ulm hydraulic specialists is being used in a broader and broader range of applications.

Kramer Allrad is achieving more speed in its 80s range thanks to the ICVD drive from Sauer Bibus, under the designation "Ecospeed Fast Gear Drives“. Norbert Mingau, Product Manager at Kramer-Werke GmbH, Pfullendorf, explains: "We are already offering the Ecospeed Fast Gear Drives, based on the ICVD technology from Sauer Bibus, for our 80s wheel loaders from model 380. In addition to improved operating comfort, Kramer customers also get the joy of using a wheel loader with trailer attachment as a fully-fledged tractor truck, which also has the EC tractor permit for use of public roads." Sennebogen uses the ICVD drive from Sauer Bibus for its Multiloader 310. We achieve a clear improvement when using the ICVD in our multiloader, particularly due to improved drive features. Thus, we can offer our customers additional benefits, which gives us a competitive advantage", says Udo Thiess, Project Leader Multiloader, at SENNEBOGEN Maschinenfabrik GmbH, Straubing, on use of the high speed drive. The ICVD drive from Sauer Bibus is also offered by the Italian telescopic handler manufacturer DIECI in ist machines under the name "VS", which stands for "Vario System".

No.3 / October 2010

Ralf Schrempp – the Managing Director of Sauer-Bibus - is convinced that the success will continue, as the concept of the ICVD is designed for the future. There will be more and more machines with hydrostatic drive, for which the drive speed will play a decisive role for cost-effective use.

Photos

Picture 1 - ICVD drive with large-angle technology. The large adjusting range up to 45 ° allows continuous drive regulation up to a speed of 80 km/h.

Picture 2 – Kramer photoA Kramer wheel loader can be used as a fully-fledged tractor truck with road permit with the Ecospeed Fast Gear Drive.

Picture 3 – Sennebogen photo Multiloader 310The Multiloader from Sennebogen with ICVD drive technology from Sauer Bibus.

Picture 4 – DIECI photoThe Italian telescopic handler manufacturer DIECI also relies on the ICVD technology of SAUER BIBUS. The vehicles are equipped with this drive technology under its "VS" label, which stands for "Vario System".

The BIBUS Group sees itself as best equipped to give technological support for the development of modern and efficient machines with powerful drive systems, as an expert partner for construction and agricultural machine manufacturers.

29

30

No.3 / October 2010

INVESTIGATIONS OF GAS FORMATION IN SMALL WASTEWATER TREATMENT SYSTEMS

Dr.-Ing. Elmar Dorgeloh*, Dipl.-Ing. Patricia Khan*

*Prüf- und Entwicklungsinstitut für Abwassertechnik an der RWTH Aachen e.V. (PIA e.V.)Mies-van-der-Rohe-Str. 1, 52074 AachenE-mail: Dorgeloh@pia.rwth-aachen.de

Khan@pia.rwth-aachen.de

1 Basic InformationDuring wastewater treatment under anaerobic conditions, a gas mixture is generated from the decomposition of organic materials, consisting of around two thirds of methane and one third of carbon dioxide. Furthermore, small amounts of other gasses, such as hydrogen sulphide may be present [1]. For nearly all currently operated systems for the decentralised treatment of domestic wastewater, anaerobic operating conditions can occur. The organic load of the domestic wastewater is a potential cause for fouling processes. Methane is classified as a hazardous gas by the EU-Ordinance on Hazardous Substances [2]. It is a highly flammable gas, which can form highly explosive mixtures with air, or respectively oxygen.

Table 1:Zone Classification Explosive Areas [3]

The explosive range lies between 4.4 and 16.5 vol.% methane in air with a maximum of the explosion force at 9.4 vol.% methane in air. Mixed with strongly oxidising gasses, an explosion may occur spontaneously or with thermal as well as catalytic ignition. [2]The Ordinance on Industrial Safety and Health, in Germany [3], stipulates that employers must ensure the issuance of an explosion protection document December 2005 for work equipment and procedures in explosive areas. The issuance of an explosion protection document is based on a risk assessment. The explosive areas are subdivided into zones, which are distinguished by the frequency and duration of the hazardous explosive atmosphere. The zone classification is summarised in the following table.

No.3 / October 2010

The Ordinance on Industrial Safety and Health defines the terms explosive atmosphere and hazardous explosive atmosphere as follows [3]:

§ Explosive atmosphere:Mixture of air and flammable gasses, fumes, mists or powders under atmospheric conditions, during which the combustion process is transferred to the entire unburnt mixture after ignition.

§ Hazardous explosive atmosphere:Explosive atmosphere, which occurs in such a quantity (risk-impending amount), that special preventive measures are necessary to maintain the protection of the safety and health of the employees and others.

The Ordinance on Industrial Safety and Health contains criteria for the selection of equipment and protection systems for explosive areas. As long as the explosion protection document, based on the risk assessment, does not state otherwise, the following categories of equipment are to be used in dependence of the zones (according to the guideline 94/9/EC [4]):

§ Zone 0: equipment from category 1§ Zone 1: equipment from category 1 or

category 2

§ Zone 2: equipment from category 1, category 2 or category 3

The categories determine specifications concerning the prevention of ignition sources and surface temperature as well as, for categories 1 and 2, concerning the unclosing of equipment parts. This ensures different securities for different application areas.

The explosion protection regulations (GUV-R 104, part 1 [7]) describe measures of explosion protection, which are distinguished according to the following division and priority:

§ Measures which prevent or constrict the formation of a hazardous explosive atmosphere (prevention of an explosive atmosphere, E 1)

2 Methane MeasurementsTo estimate the explosion r isk, gas measurements were carried out of the PIA [8] in small wastewater treatment systems. These examinations were carried out under laboratory conditions as well as on site of operating treatment systems in 2006.

2.1 Description of the Measuring SystemThe methane measurements were carried out with the gas warning system WinPro® by Winter G m b H . T h e s e n s o r s f o r m e t h a n e measurements are based on the principle of optical detection of gases using infrared frequencies. The sensors are constructed for the standard measurement range of 0 to 100% of the lower explosive limits (LEL). The lower explosive limit corresponds to the lower limit of the explosive range of 4.4 vol.% methane in air. The existing measurement technology allowed for a continual data recording. The recording of the measuring values was usually made every 5 minutes. To evaluate the selected time interval, a temporary interval of 30 seconds was set during the measurements on the PIA testing field. Since the results were similar, the remaining examinations were made at an interval of 5 minutes.The evaluation of the collected data was made in dependence of the frequency of the differently classified measuring values. The selected classifications for methane are orientated at the standard alarm thresholds of gas warning systems [1]:

§ Measures which prevent the ignition of a hazardous explosive atmosphere (prevention of active ignition sources, E 2)

§ Measures which constrict the impact of an explosion to a harmless degree (constructive explosion protection, E 3)

Fig. 3 of the outlook shows the flow chart for the evaluation of the explosion risk and the determination of protection measures.

31

No.3 / October 2010

0 to 10% LEL CH4

10 to 20% LEL CH4

20 to 50% LEL CH4

50 to 100% LEL CH4

The area from 0 to 10% LEL is to be viewed as noncritical. Between 10 and 20% of the LEL, measures may be taken to prevent the formation of an explosive atmosphere; above 20% LEL these measures should take place. Above 50% LEL, these measures should be expanded and a shut-down of all not explosive-proof electrical systems and equipment should take place [1].

2.2 Methane Measurements in Test Facility of PIA's Testing FieldA black plastic tank (reactor) was used as the PIA test facility. All openings of the tank were closed and sealed extensively. The feed line for wastewater was placed underneath the water surface. The tank was not embedded into the soil, so that the temperature impact could be observed. Methane has a lower density than air and should therefore rise to the top.

Digester gas however, is a homogenous mixture of different gasses, which does not separate according to different densities because of its frequent mixing [1]. Therefore, experiments were made with varying measuring points. Two methane sensors were installed at different heights (0.14 and 0.74 m underneath the lid bottom). The test plant was filled with ca. 600 litres of raw wastewater. In the first two months of the examination period, 50 litres of wastewater were discharged and 50 litres of fresh wastewater were added manually three times per week. Afterwards, 50 litres were exchanged only once per week. Because of the feed connection pipe, the lid of the tank did not need to be opened to fill the tank.

To evaluate the methane measurements, the distribution of the measuring values of the two installed methane sensors as well as the average day temperatures are taken into account. The following figure depicts the phase with the maximum methane loading which could be detected within the framework of the data recording.

Fig. 1:Test Reactor at PIA Facility - Cross Section [6]

32

No.3 / October 2010

Fig. 2:Maximum Load – Methane Test Facility [6]

The gas measurements in this test facility have shown that a hazard potential concerning gas formation can exist with certain boundary conditions.

3 Summary The examinations of several small wastewater treatment systems on the PIA testing field, on site of private operators and on a test plant have shown that, during normal operation, no or only very little methane formation can be observed. The majority of the measured values lies in the range beneath 10% LEL. The values which exceed 10% LEL represent temporary peaks and no permanent elevation of the methane level. Phases with practically constantly elevated methane contents, between 10 and 20% LEL, were only observed in a plant on the PIA testing field. A reduction of the ventilation of this plant led to a rise in the measured values up to a maximum value of nearly 70% LEL, whereas the test plant did not show any significant changes after a reduction of ventilation. In different testing phases, only small amounts of methane formation were observed.

The methane measurements in a further testing plant have shown, that given certain boundary conditions, a danger potential concerning gas formation is possible. The methane formation during these experiments was influenced by the operating conditions (nearly no ventilation) and temperature (tank above ground). During favourable conditions for methane formation, continual data above 20% LEL and maximum

values up to 35% LEL were recorded. The arrangement of methane sensors at different heights has shown that the methane content is mostly higher in the upper area and methane bubbles form even though the bottom area, near the water surface, showed no methane present.

The examinations have shown that no or only very low methane formation can be observed during the normal operation of small wastewater treatment systems. Furthermore, several factors which influence the formation of methane could be ascertained. For one thing, the operating conditions are crucial. The guarantee of sufficient ventilation is an important protection measure for the prevention or constriction of the formation of a hazardous explosive atmosphere.

33

No.3 / October 2010

A further essential influence factor is the temperature. Advantageous conditions for the formation of methane are wastewater temperatures of above 30 °C. These temperatures are usually not reached by wastewater treatment systems installed underground. Furthermore, differences concerning the plant type were determined. In especially ventilated tanks, such as membrane bioreactors, the formation of methane is practically impossible. A danger potential is possible given during non-ventilated treatment steps. In addition, differences were observed which can be led back to plant-specific influences. During the examination of two primary treatment systems in the identical time frame on the PIA testing site, very different methane formations were observed. In one system, virtually no methane was measured whereas the other showed regular peaks of 5 to 12% LEL. However, it was not possible to determine the cause for these peaks. The occurrence of regular, short peaks of methane formation between 5 and 20% LEL was observed in numerous cases.

In view of the methane measurements of the examined, properly operated small wastewater

treatment systems on the PIA testing field, a maximum value of 22% LEL was recorded. On this basis, the occurrence of a hazardous explosive atmosphere in the sense of the Ordinance on Industrial Safety and Health cannot be observed.

The methane measurements in the scope of this project have allowed for the following classif ication of the examined small wastewater systems to be made. The flow chart shows how the explosion danger is appraised and how the protection measures are appointed [5].

Literature[ 1 ] DWA-Arbe i t sbe r i ch t – E rs te l l ung von

E x p l o s i o n s s c h u t z d o k u m e n t e n f ü r abwassertechnische Anlagen; DWA Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V.; September 2005

[2] EG-Sicherheitsdatenblatt gemäß TRGS 220, Methan; Februar 2005

[3] Betriebssicherheitsverordnung – Verordnung über Sicherheit und Gesundheitsschutz bei der Bereitstellung von Arbeitsmitteln und deren Benutzung bei der Arbeit, über Sicherheit beim Betrieb überwachungsbedürftiger Anlagen und über die Organisation des betrieblichen Arbeitsschutzes; vom 27. September 2002, in der Fassung vom 25. Juni 2005

[4] ATEX-Produkt-Richtlinie (RL 94/9/EG)- Geräte und Schutzsysteme in explosionsgefährdeten Bereichen; vom 23. März 1994

[5] Explosionsschutz-Regeln (EX-RL) – Regeln für das Vermeiden der Gefahren durch explosionsfähige Atmosphäre, GUV-R 104; Bundesverband der Unfallkassen; März 2005

[6] ISA. PIA - Abschlussbericht zum Forschungsvorhaben „Untersuchungen zur Gasentwicklung in Kleinkläranlagen (Abschätzung des Explosionsrisikos)“AZ IV - 9 - 042 063, für das Ministerium für Umwelt und Naturschutz, Landwirtschaft und Verbraucherschutz des Landes Nordrhein-Westfalen, Aachen Dezember 2006

34

No.3 / October 2010

Fig. 3:Classification of the examined Small Wastewater Treatment Systems [6]

35

CONTROL OF WATER TURBINE GUIDE APPARATUS BY USE OF WATER HYDRAULIC ACTUATOR

36

No.3 / October 2010

* Cracow University of Technology Institute of Machine Design - Fluid Power LaboratoryAl. Jana Pawla II 37, 31-864 Krakow, PolandEmail: walczakp@mech.pk.edu.pl, sobczyk@mech.pk.edu.pl

ABSTRACT: This article presents development work on creating the model of the water hydraulic control system for water turbine guide apparatus control. Complete was added to hydraulic system model of relief valve and piston pump. Also some data from typical water turbine control system was taken into account. Therefore presented model of control system is closer to reality for small water-power plant. The test of describing the mass of cylinder - guide apparatus - blade was conducted. Reduced mass of such mechanism is a function of cylinder position. Paper shows proposal to implement turbine rpm control which will be responsible for increasing or decreasing of water flow on turbine blades to keep its set velocity. It should allow omitting electronic system i.e. based on PID or fuzzy logic controller which are used today to steering and monitoring turbines of water-power plant. This research has big meaning in development of small water turbine

Keywords: Cylinder Control, Simulation, Water Turbine Guide Apparatus, Reduced Mass

PhD student Pawel WALCZAK* and Dr., MS. Eng. Andrzej SOBCZYK*

IntroductionEnergy of water and wind has been widely employed for a long time. These resources are inexhaustible, although their distribution is rather irregular. Since the Roman times water power has been harnessed to drive corn mills and later sawmills, fulling mills, ore mills in ironworks and forging hammers. Towards the end of the medieval period, some of these plants were able to deliver power of the order of tens of kilowatts. Water- wheels and windmills prompted the onset of the first industrial revolution. Nevertheless, we are now able to utilize only 15% of their energy potential. Power ratings of typical power stations nowadays are given in MW, the energy efficiency being 90-95%. The operating principle has not changed much since the old days, though now water drives the blades in water turbines, which in turn trigger the generators. The construction of a hydropower plant is now restricted only by the requirements imposed by site-specific and geological conditions and the financial resources available to the investor. Plant buildings and hydropower facilities are most expensive to build, other equipment proves to be less costly. The annual operating costs of a hydropower plant account for about 0.5% of the total capital expenditure.

ContinuationThis article is a continuation of a paper “Control system of a double-acting, single-ended cylinder simulation- concept of water turbine

thguide apparatus control” presented on the 5 symposium in Krakow in 2008. The paper provided the general concept of a purely hydraulic system for controlling the guide apparatus in a low-power water turbine which, like any other electronic system, would maintain the constant turbine speed under variable loading and in backwater. Through the flow rate control, the system shall change the position of blades in the guide apparatus so that it should supply the correct volume of water onto the turbine blades. That configuration allows for eliminating intricate control and monitoring systems supported by various pressure sensors, PID controllers or fuzzy logic. The additional goal is to simplify the structure of the control system, to ensure its easy maintenance and to reduce costs involved in the hydraulic control system.In its previous version, the system used for modeling and simulation would comprise a pump, a relief valve, a direction control valve, a throttle valve and a cylinder. Of key importance is the model of the cylinder-loading force characteristic as it allows for emulating the

No.3 / October 2010

The equation of motion of the cylinder under the action of the hydrostatic force and under the changeable load has been modified to improve the accuracy of calculations.

( ) 21 uuotp FFFFFvm

dt

d----=×

An essential requirement for a correct model is to know the proper mass. This paper addresses how the reduction of mass was of the guide apparatus's blade system is determined.

3. Theoretical backgrounds

The energy approach is used to find the mass of the system reduced to a point at the end of the piston rod. Kinetic energy of the mechanism in a plane motion is given as:

(1)

(2)

(4)

(5)

(3)

( )å=

×+×=k

iiiSii JvmE

1

22

2

1w

When an arbitrary reduction point X (point A in Fig. 4) of known velocity v is chosen to which x

the mass of the entire mechanism m is to be zr/x

reduced, the condition of equality of kinetic energy has to be fulfilled:

2

/2

1xxzr vmE ×=

å= ú

ú

û

ù

êê

ë

é

÷÷ø

öççè

æ×+÷÷

ø

öççè

æ×=

k

i x

ii

x

Siixzr

vJ

v

vmm

1

22

/

w

Accordingly, we get:

DataTo determine the reduced mass requires a model of the guide apparatus system. The model is created in Solid Works based on available data and technical specifications of a ready-made guiding system. Data on hydraulic components and force values come from the project undertaken by the CEDI company in collaboration with the Fluid Power Laboratory in the Institute of Machine Design.

Fig. 1: Diagram of the complete Francis turbine

Fig. 2: Model of the guide apparatus system developed in Solid Works

Figure 2 shows a model of the guide apparatus in a turbine, simplified to facilitate the calculation procedure. The model incorporates two fixed rings which represent the points where the blades and the cylinder are attached. There is also a guiding wheel, which sets the blades in motion, driven by the cylinder, 20 blades and 20 levers connecting the blades with a guiding wheel.

By observing the Solid Works model, Eq (4) can be rewritten as

úú

û

ù

êê

ë

é

÷÷ø

öççè

æ×+

úú

û

ù

êê

ë

é

÷÷ø

öççè

æ×+÷÷

ø

öççè

æ×+

úú

û

ù

êê

ë

é

÷÷ø

öççè

æ×=

2

33

2

22

2

22

2

11/ 2020

AAAA

Azrv

Jv

Jv

vm

vJm

www

Certain data, particularly the length of conduits and the rate of increase of the loading force need some corrections and modifications.

operating characteristic of the machine or of its selected components, depending on the applied formulas.

37

No.3 / October 2010

Where: subscript 1 designates guiding wheel, 2 – lever, 3 – blade.

Other parameters needed include masses, moments of inertia, and angular velocities of system components. As the model is developed in Solid Works, its functions can be explored to compute the mass and moment of inertia of the system components based on their shapes and material density. This simplifies the process and because of intricate geometry is more accurate.Since the system runs on water, its components have to be made of water-resistant steel, its

3density is taken to be 7860 kg/m .

The remaining parameters, such as linear and angular velocities of particular components required to find the reduced mass of the system can be obtained using the kinematic analysis of the guide apparatus system.

Fig. 3: Model of the guide apparatus system – top view

Table 1: Data required obtaining m in Solid Workszr

5. Kinematic analysis

System shown in Fig. 3 could be presented by below kinematics scheme.

5.1 Wheel Based on this schematic (Fig. 4) with assumption that velocity of cylinder movement is known (from VisSim simulation) angular velocity of guide apparatus wheel could be determined:

acos×= vv A

AB

v A=1

w

aw cos1 ×=

AB

v(8)

(10)

(11)

(12)

(13)

(14)

(9)

(7)

(6)

5.2 Lever Determine the linear velocity of point C:

BC

v

AB

v CA ==1w

AC vAB

BCv ×=

Determine the angular velocity of link CD:

CDv

C

CO

v=2w

ACDv

vABCO

BC×

×=

2w

Determine the linear velocity of point S : 2

CD

v

S

OS

v

2

22 =w

ACDv

CDv

S vABCOOS

BCv ×

××=

2

2

38

No.3 / October 2010

S2

OvCD

v

vc

O

w1

vS2vD

vA

B

A

C

E

D

w2 w3

Fig. 4: Kinematic scheme of guide apparatus system with vectors of linear velocities and

angular velocities

5.3 BladeDetermine the linear velocity of point D:

CDv

DCDv

C

DO

v

CO

v==2w

ACDv

CDv

D vABCO

BCDOv ×

×

×=

(15)

(16)

(17)

(18)

(19)

Determine the angular velocity of link ED:

DE

v D=3

w

ACD

v

CDv

vABCODE

BCDO×

××

×=3w

( )( )2

2

322

2

2

2

1

/

20

AB

DE

DOJJ

OS

m

CO

BCJ

m

CDv

CD

v

CDv

Azr

÷÷÷

ø

ö

ççç

è

æ

÷÷

ø

ö

çç

è

æ×++

÷÷

ø

ö

çç

è

æ×+

=

5.4 Reduced MassFinally Eq. (5) can be rewritten as

Conclusion

Dur ing the cy l inder movement the instantaneous centre of rotation changes

CDposition that is why the distances |CO |, vCD CD|DO |, |S O | depend on |AO|. A position of v 2 v

CD the instantaneous centre of rotation O can be v

determined based on the law of cosines, thetriangles' similarity and the definition of the area of triangle.Due to significant complication of the reduced mass calculation, results of the final equation solution are not inserted in this paper. After replacing the reduced mass in Eq (1) velocity and displacement of the cylinder piston rod may be impossible to calculate. For now, simpler analytic methods will be used to determine the instantaneous centre of rotation. Also the possibility of the use of an average reduced mass should be considered. It would be calculated as an average of the reduced mass in the final and some intermediate points of the piston rod positions. In this case the instantaneous centre of rotation could be determined using a graphical method.

The research program involves the development of a simulation model in the program VisSim. Extensive tests will show which solution of the control system should meet the project objectives, i.e. provide sufficiently short response time of the cylinders in the cylinder of guide apparatus.

39

No.3 / October 2010

That would enable the optimal structure for the system to be chosen, followed by system design and selection of its major components, supported by calculations to check the accuracy of the assumptions. Finally, a real test rig will be constructed.

In the context of current trends in construction of small-scale hydropower plants, the electric equipment should be extended such that the plant operation should be automatic. However, that requires dedicated software, well-qualified personnel and high maintenance and servicing costs

The novel feature in this study is an attempt to answer the question whether the construction of a purely hydraulic system be possible and an economically viable option. Still exists the possibility that such a system may prove impossible to build in the light of the underlying assumptions. In such case the study should pave the way to future solutions to seek another approach to hydraulic control of the guiding apparatus in water turbines.

7.LIST OF NOTATIONS

E Kinetic energy J Fp Hydrostatic force N Fo Load force N F t Resistance force N Fu1, Fu2 Impact forces N J i Moment of inertia of i element kg·m

2

OvCD

Instantaneous centre of rotation m Reduced mass of guide apparatus system and mass of piston kg mzr/x Reduced mass of guide apparatus system kg mi Mass of i element kg v Piston velocity m/s vsi Velocity of centre of mass of i element m/s vx Velocity vx in reduction point m/s wi Angular velocity of i element rad/s

REFERENCES

van Antwerpen H.J., Greyvenstein G.P. (2005). Use of turbines for simultaneous pressure regulation and recovery in secondary cooling water systems in deep mines, Energy Conversion and Management 46, pp. 563–575. Garbacik, A. (1997). Studium projektowania układów hydraulicznych. Ossolineum, Krakow.Kishora N., Saini R.P, Singh S.P. (2007). A review on hydropower plant models and control. Renewable and Sustainable Energy Reviews 11, pp. 776–796.Schönborn A., Chantzidakis M., (2007). Development of a hydraulic control mechanism for cyclic pitch marine current turbines, Renewable Energy 32, pp. 662–679.Sobczyk, A.; Walczak, P. (2007). Control system of double acting single ended cylinder simulation – concept of Water Turbine guide apparatus control lubrication. 5th PhD Symposium, Krakow, pp. 524–533.Stryczek, S. (1995). Napęd hydrostatyczny. WNT, Warszawa.Trostmann, E. (1996). Water hydraulic Control Te c h n o l o g y . M a r c e l D e k k e r , I N C .Walczak, P. (2006). Symulacja cyfrowa i badania charakterystyk przekładni hydrostatycznej. Krakow.

40

41

No.3 / October 2010

AbstractThe large number of parameters affecting the hydraulic seal performances induces significant difficulties in modeling and understanding their behavior. This paper describes a methodology used to perform a correct computation of the static contact pressure between the seal and the rod. The computation of static dry pressure profile and contact length is made by means of commercial FEA software. The non-linear elastomer stress-strain behavior is taken into account by using different strain-energy-potential laws. The results show that the best model is the so called "second-order polynomial" model. However, the linear or the Mooney-Rivlin models induce errors inferior at 2% (if the normal contact force is the comparing criterion).

Keywords: Elastomeric Seals, Rod Seals

EVALUATION OF THE ELASTOMER HYPER ELASTIC BEHAVIOR A U-CUP HYDRAULIC ROD SEAL

1 2 1 2 2A. Fatu , M. Crudu , M. Hajjam , S. Cananau , A. Pascu

1PPRIME Institute, CNRS – University of Poitiers - ENSMA UPR 3346Mechanical Engineering, Structures and Complex Systems Department, Poitiers, France2Machine Elements and Tribology, University “Politehnica” of Bucharest, Romania

INTRODUCTION

The elastomeric seal is one of the simplest seal designs used in hydraulic systems. Its role is critical in hydraulic assemblies for obvious safety and environmental reasons. In spite of its technological simplicity, modeling a hydraulic seal is not easy. The difficulties come from the large number of variables significantly affecting sealing performances.

Many studies have been published on hydraul ic seals in recent decades. Researchers White and Denny might be considered as the pioneers in this field, according to the publications of Nau [1] and Nikas [2]. Their work dated from 1947 and launched the research into the understanding of the behavior of reciprocating seals.

The first difficulty in modeling elastomeric seals is attributed to the non-linear stress-strain elastomer elastic behavior. Therefore, even if there still are many publications in the literature utilizing the linear stress-strain model, the non-linear models are more and more adopted. Nikas and Sayles systematically consider the most popular non-linear (Mooney Rivlin) model in analyz ing reciprocat ing seals at temperatures between -54 and +135 °C. [3-6].

Kanters et al. [7] compare uniaxial extension experimental data with numerical predictions according with the neo-Hookean and Mooney-Rivlin model. It is shown that Mooney-Rivlin model is clearly superior to the neo-Hookean model. However, a second radial stiffness experiment indicates same differences between Mooney-Rivlin prediction and the experimental data.

Starting from a simple uniaxial tension test, this paper is focused on choosing the constitutive approach able to evaluate the elastomer hyperelastic behavior.

STATIC COMPUTATION OF CONTACT FORCES AND PRESSURE PROFILES

The first step in a theoretical analysis of hydraulic elastomeric seals is the computation of static dry pressure profile and contact length. The main problem is the non-linear elastomer stress-strain behavior. Moreover, their mechanical properties strongly depend on temperature and can change in time as they age. The numerical models usually deal with incompressible, hyperelastic (rubber-like) materials and express the mechanical properties in terms of a "strain energy potential", W, which defines the strain energy

No.3 / October 2010

stored in the material per unit of reference volume (volume in the initial configuration) as a function of the strain at that point in the material. Mainly, there are 3 forms of strain energy potentials used in the literature to model approximately incompressible isotropic elastomers: the Ogden, the Mooney-Rivlin and the Neo-Hookean model, with a strong preference to the Mooney-Rivlin model.

In this paper, the start point in choosing the best model to use is an experimental uniaxial tension test data. This is in fact the easier way to obtain test data that give information about the material behavior. To obtain a complete characterization of rubber-like materials, supplementary biaxial tension, planar tension, shear and volumetric test data are necessary. Furthermore, all this must be made for different temperatures.

Knowing that only the uniaxial tension test data has been available to go about this work, the next section is focused on obtaining the best constitutive approach for the studied seal material.

es

0

te

F

Ss =

l

Le

D=

The engineering strain ( ) is obtained by dividing the sample elongation ( ) with the initial length of the test sample (L):

e

(1)

(2)

(3)

lD

On the same figure 1, the variation of the real stress with can also be observed. The real stress is obtained by dividing with the real cross-sectional area (S):

Ft

s e

tF

Ss =

0

( )

S LS

L L=

+ D

where, for an incompressible material

0 0.1 0.2 0.3 0.4 0.5

Engineering Strain, e

0

2

4

6

Str

ess

,s

[MP

a]

Engineering (apparent) stress

Real stress

0 0.5 1 1.5 2 2.5 3

Engineering Strain, e

0

20

40

60

80

Str

ess

,s

[MP

a]

Engineering (apparent) stress

Real stress

a) b)

Figure 1: Uniaxial tension stress-strain curve

E x p e r i m e n t a l v e r s u s n u m e r i c a l investigation

Figure 1a) shows the stress-strain curve obtained by the uniaxial tension test. The engineering (also called apparent) stress ( ) is obtained by dividing the tension force ( ) with Ft

The real stress variation with obviously shows a rubber-like stress-strain behavior. How it can be seen later in this paper, the maximal strain computed in the analyzed seal, after mounting and pressurization, didn't exceed 0.5. Consequently, figure 1b) shows the stress-strain experimental data used to identify the most appropriated hyperelastic strain energy potential model.

e Modern FEM software, allows to evaluate hyperelastic material behavior by automatically creating response curves using selected strain-energy-potential models. In order to evaluate the optimal strain energy potential law, the experimental test data are entered in ABAQUS software and the tension test is simulated. Figure 2 shows the FEM model used to simulate the tension test.

42

No.3 / October 2010

Encastre zone Applied

load

Displacement measurement

Rigid material

Hyperelastic material

Figure 2: FEM model of the tension test

Several constitutive models are used and the results are compared with the experimental data. The numerical results are presented for Ogden, Mooney-Rivlin and Neo-Hookean models. A fourth model is also used: the second-order polynomial model. In fact, Mooney-Rivlin and Neo-Hookean models can also by called polynomial models. The general form of a polynomial model is:

2

1 21 1

1( 3) ( 3) ( 1)

N Ni j el i

iji j i i

W C I I JD+ = =

= - - + -å å (4)

(5)

(6)

(7)

where is the elastic volume ratio, and are temperature-dependent material parameters. If the material is considered incompressible (Poisson's ratio ) the second sum in equation (4) is neglected . I and I are the first 1 2

and second deviatoric strain invariants defined as:

elJ ijC

iD

0.5n =

2 2 2

1 1 2 3

2 2 2

2 1 2 2 3 3 1( ) ( ) ( )

I

I

l l l

ll l l l l

= + +

= + +

where (i=1,2,3) are the deviatoric stretches (ratio of deformed to reference length). If N = 1 the polynomial model becomes the Mooney-

Rivlin model:

il

10 1 01 2( 3) ( 3)W C I C I= - + -

Also, if C is set to zero, equation (6) gives the 01

Neo-Hookean model:

10 1( 3)W C I= -

Figure 3a) shows the stress-strain variation for different strain energy potential laws, for a positive strain. The best fit between the numerical results and the test data is obtained for Ogden and second-order polynomial models. The worst model is the Neo-Hookean model.

a) b) 0 0.1 0.2 0.3 0.4 0.5

Engineering Strain, e

0

1

2

3

4

Str

ess

,s[M

Pa]

OgdenMooney-Rivlin

Neo-Hookean

Polynomial 2-degree

Experimental data

-0.5 -0.4 -0.3 -0.2 -0.1 0

Engineering Strain, e

-14

-12

-10

-8

-6

-4

-2

0

2

Str

es

s,s

[MP

a]

Ogden

Mooney-RivlinNeo-Hookean

Polynomial 2-degree

Figure 3: Stress-strain variation for different strain energy potential laws a) positive strain b) negative strain

43

No.3 / October 2010

Considering that hydraulic seals work essentially under compression, figure 3b) shows the numerical results obtain for compressive loading. It can be observed that the four models show significant differences for the compression test. This raises some questions about the validity of the numerical model in compression.

Supposing that the elastic behavior of the elastomer is identical in compression and in tension, the real stress variation for negative strains can be obtained from the positive test data by supposing an anti-symmetric behavior.

Furthermore, a theoretical engineering stress variation can be calculated for both positive

a)

b)

-0.5 -0.4 -0 .3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

Engineering Strain, e

-12

-8

-4

0

4

8

Str

es

s,s

[MP

a]

Engineer ing (apparent) stress

Real stress

0 0.1 0.2 0.3 0.4 0.5

Engineering Strain, e

0

1

2

3

4

Str

es

s,s

[MP

a]

Ogden

Mooney-RivlinNeo-Hookean

Polynomial 2-degree

Experimental data

-0.5 -0.4 -0.3 -0.2 -0.1 0

Engineering Strain, e

-14

-12

-10

-8

-6

-4

-2

0

Str

es

s,s

[MP

a]

Ogden

Mooney-RivlinNeo-Hookean

Polynomial 2-degree

Experimental data

c)

and negative strains and then entered in the FEM software (Figure 4a).

Figure 4b) and 4c) shows the stress-strain variation for different strain energy potential laws, for numerical predictions obtained with a complete negative-positive engineering stress data. The best fit is obtained for the second-order polynomial model. The Ogden model, that fits very well the experimental data in tension, seems to have some difficulties in evaluating both extension/compression solicitations. Consequently, the second-order polynomial model will be used in modeling the seal static behavior.

Figure 4: a) Stress-strain curve for identical tension-compression behavior

b) Stress-strain numerical behavior for a positive strain

c) Stress-strain numerical behavior for a negative strain

44

No.3 / October 2010

FEM model of the seal

The FEM model of the rod seal is presented in figure 5. The seal is meshed with reduced integration axisymmetric stress elements. The computations are made in large displacement and deformation hypotheses. The rod and the seal housing are usually made in more rigid material (typically steel) than the elastomeric seal. Consequently, it is reasonable to consider the rod and the seal housing as analytical defined rigid elements. Friction boundary conditions are applied on the seal/rod and seal/housing interfaces.

Before assembling

After assembling

Rod surface

Seal housing

Oil side

instroke outstroke

pcyl

Air side

Figure 5: FEM model of the rod seal

Closely to the contact zones, the seal is meshed with structured quadratic elements, usually used in treating contact problems.

A negative radial displacement of the seal, followed by a positive radial displacement of the rod is the first modeling step. Secondly, a constant hydraulic pressure p is applied in the cyl

oil side for all surface elements that are not in contact with the rod or the housing. The initial inner radius of the seal is 12 mm and increases to 12.5 mm after mounting. The initial outer radius is 18 mm and decreases to 17.5 mm after mounting.

45

No.3 / October 2010

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6Contact length, L [mm]

0

1

2

3

4

5

6

7

8

9

10

11

12

Co

nta

ctpre

ssu

re,p

co

nt[M

Pa]

Average elements length in contact zone

2 µm4 µm

6 µm10 µm

Figure 6: Contact pressure distribution for different average length of the elements in contact zone between the seal and the rod

Figure 6 shows the contact pressure variation with the contact length for p = 10 MPa and for cyl

different average lengths of the elements in contact with the rod surface. The computations are made for a friction coefficient f between the seal and the housing of 0.1 and for a frictionless contact between the seal and the rod surface. It can be observed that the contact pressure distributions for the various element lengths are almost identical. In order to compare the results, the contact normal force is computed by:

contF

0

2L

contF R pdxp= ò where R = 12.5 mm (8)

Table 1 shows the contact forces computed for the four cases. It can be observed that a length mesh of 6 or 10 µm can induce errors up to 3 .18%. Consequent ly, the fo l lowing computations are made for average element lengths of 4µm. The choice made here will be supported in a later hydrodynamic computation of the seal behavior.

Table 1: Contact normal force for different average length of elements in contact zone

By comparison with the second-order polynomial model, several computations have been made in order to investigate the error on the contact force induced by the classic linear theory of elasticity and the Mooney-Rivlin model. The Young modulus used in the linear model is computed by fitting the real stress-strain curve between 0 and 0.5 strain.

46

No.3 / October 2010

Figure 7: Contact pressure distribution for three constitutive models

pcyl = 5 MPa pcyl = 10 MPa pcyl = 20 MPa

Model Fcont (N) Error % Fcont (N) Error % Fcont (N) Error %

Classic linear

(E=11 MPa) 2357.2 1.56 4634.8 1.33 8917.8 1.04

Mooney-

Rivlin 2389.2 0.22 4663.7 0.69 8876.4 1.49

Second-order

polynomial 2394.6 0 4697.1 0 9011.2 0

Table 2: Contact force for different constitutive models, for three hydraulic pressures

47

No.3 / October 2010

Figure 7 shows the contact pressure distribution for a hydraulic pressure of 5 MPa, 10 MPa and 20 MPa. Table 2 shows the computed contact forces for the three cases. The differences observed are smaller than 2%. The results agree with previous researches, where the use of linear or Mooney-Rivlin models are proved to be sufficient in treating reciprocating elastomeric seals.

CONCLUSIONS

The paper deals with choose the best strain energy potential law in modeling the hyperelastic behavior of the studied elastomeric seal. The start point is a simple uniaxial tension test data. Using different strain energy potential approaches, the tension test is simulated by means of a FEM software. The comparisons between numerical and experimental data show that the model that best fits the numerical data is the so called second-order polynomial model. Knowing that almost all published numerical studies on hydraulic seals use the classical linear or the Mooney-Rivlin models, a comparison is made regarding the predicted static contact force between the seal and the rod. The global differences are smaller then 2%.

Two distinct approaches are generally used to evaluate the sealing performances of hydraulic seals: the inverse EHL method and the direct EHL approach. Both methods have, as a starting point, the contact pressure distribution between the seal and the rod. Therefore, small errors in the computation of the contact pressure distribution can lead to important differences concerning power loss friction and leakage predictions.

ACKNOWLEDGMENT

We like to thank for the financial support in performing this work to Technical Centre for Mechanical Industry - Sealing Technologies Department (Pôle Technologies de l'Etanchéité, CETIM, Nantes).

Also, we like to thank, for their technical support, to INOE2000-IHP, BUCHAREST, ROMANIA.

The work has been supported by the Sectoral Operational Programme Human Resources Development 2007-2013 of the Romanian Ministry of Labour, Family and Social Protection t h r o u g h t h e F i n a n c i a l A g r e e m e n t POSDRU/88/1.5/S/61178.

REFERENCES[1] Nau, B.S., (1999), “An historical review of studies of polymeric seals in reciprocating hydraulic systems”, Proc. Mech. Eng., Part J, 213, pp. 215-226.[2] Nikas, G.K. (2009), "Eighty years of research on hydraulic reciprocating seals: review of tribological studies and related topics since the 1930s", Proc. in Mech. Eng., Part J, 224, pp. 1-23. [3] Nikas, G. K. and Sayles, R.S., (2004), “Nonlinear elasticity of rectangular elastomeric seals and its effects on EHD numerical analysis”, Tribol. Intern. 37, 8, pp. 651-660.[4] Nikas, G. K. and Sayles, R.S., (2006), “Computational model of tandem rectangular elastomeric seal for reciprocating motion”, Tribol. Intern. 39, 7, pp. 622-634.[5] Nikas, G. K.., (2004), “Theoretical study of solid back-up rings for elastomeric seals in hydraulic actuators”, Tribol. Intern. 37, 9, pp. 689-699.[6] Nikas, G. K., (2003), “Transient EHD lubrication of rectangular elastomeric seals for linear actuators”, Proc. in Mech. Eng., Part J, 217, pp. 461 - 473.[7] Kanters A.F.C., Verest J.F.M. and Visscher M., (1990), "On reciprocating Elastomeric Seals: Calculation of Film Thicknesses Using the Inverse Hydrodynamic Lubrication Theory", Tribol. Trans. 33, pp. 301-306.

48

EXPERIMENTAL IDENTIFICATION OF ELECTROHYDRAULIC SERVOMECHANISMS WITH VIRTUAL INSTRUMENTS TECHNIQUE

1) 1)Ph.D.eng. Dragos Ion GUTA , Ph.D.stud.eng. Catalin DUMITRESCU , 1) 1)Ph.D.eng. Ioan LEPADATU , Ph.D.eng. Corneliu CRISTESCU

1) INOE 2000-IHP Bucharest, ROMANIA

No.3 / October 2010

Abstract: By using the methods of identification of the processes and performances of the devices of numeric calculus, the scientists and technical designers may shorten the period of development of the applications from various fields, by generating some solutions which are the proximal to reality, from the technical designing stage. These methods offer the possibility of optimization of the functional systems depending on the criteria of performance imposed. The present paper presents a generic application of dynamic identification of the electrohydraulic servomechanisms, developed and tested by the authors of the article in the compartment of general hydraulics of INOE 2000 IHP. This was developed by means of the NI LabVIEW virtual instrumentary and was successfully used by authors for determining rapidly the dymanic characteristics of the studied servosystems. Keywords: LabVIEW, electrohidraulic servomechanisms, experimental identification.

1. Virtual instrumentaryLabVIEW is a graphical programming

environment, which includes specialised functions for: data acquisition, control of instruments, the analyse of the measured data, the display and presentation of results. This offers flexibility due to a performant programming domain, without being needed to use the less performant classic programming languages

With LabVIEW may be implemented applications of data acquisitions, complex study and sophisticated data processing, all in a single programming domain, so that the performing of a specific application, on a certain platform, becomes an easy task.Unlike the programming languages of general use, LabVIEW offers to the users specific functions for the applications of measurement, control and automation, accelerating the development of complex applications. From the specific tasks of analyzing signals till the task of communication with a wide range of devices, the program allows a performant use of the systems of measurement and testing, of the systems of control and monitoring processes, being used mainly in the field of industrial order and scientific research, where are required acquisitions and complex processings of the signals. LabVIEW may be connected easily and rapidly at the measurement and control

hardware , being possible to configure and use easily a wide range of equipment, from whole devices to data acquisition plates, motion controllers, image acquisition systems or programmable automatons PLC.The application was realized modularly, being developed till now the following modules:- The module of setting up parameters of the

hardware interfaces DAQ, of the excitation signals and the processes of control and data

- The module of intermediary processing of data. The acquired signals are usually post processed and this may include a filtering, a selection of a useful zone from the vector of acquired data, the translation and conversion of parameters,etc;

Fig. 1. Graphic interface (GUI) of the module of data processing for determining the indicial answer

49

No.3 / October 2010

Fig. 2. GUI interface of the module of data processing used for determining the frequency

response

- The module for determining the indicial answer of the system(fig.1). This analyzes the signals acquired and filtered by means of the first modules and extracts automatically the information referring at the time constant value, the rise time, the transitory time of stabilization, error in stationary mode, over regulation and subregulation depending on the type of the system analyzed

Fig. 3. GUI interface of the mode of data processing for tracing the transfer spot (contour

Nyquist) and Nichols dyagram

- The module of study of the answer in frequency. If the analyzed system was excited with a sinusoidal signal of constant amplitude and variable frequency this module allows the study of the phase difference between the input signal and the output signal and the aleviation of the output depending on the frequency of the excitation signal fig2. By means of this module may be determined the passage band, the amplitude threshold, the phase threshold, the delay threshold and the module threshold

- The module of processing data for tracing the transfer spot Nyquist transfer and Nichols diagram (fig. 3). By means of the data acquired from the module of study of the answer in frequency alleviation frequency, difference of phase are traced these characteristics in the complex plan Re-Im. The information from this module may be used for studying the stability stores of the fast servomechanisms or for optimum rectification of the coefficients of the compensators of the electrohydraulic servomechanisms.

Fig. 4. The interface of the module developed for identifying the mathematical model of the

analyzed system

- The module of identification of the mathematical model of the system (fig. 4) allows the selection of the optimum module of representation of the studied system (under the form of transfer functions, of the models AR, ARX, ARMAX or the models in the field of state)and the automatic determination of

50

No.3 / October 2010

coefficients of these modules. The input information in this model are identical with the input data in the module of determining the answer in frequency. After the identification of the model may be traced a BODE dyagram of the mathematical model comparatively with that determined experimentally for finding the accuracy degree of the mathematical model identified. After validating the model this may be used for the simulated offsite study of the system.

2. Experimental identificationThe identification pursues to find the static and dynamic characteristics of processes. By identification we understand the procedure of determining a system on the base of an input and of an output, in the case of SISO systems so that this to be equivalent with the tested system. The determination of the mathematical model may be realized in 2 ways:1)by techniques of mathematical modelling

named sometimes analytic identification2)by experimental identification

In the case of experimental identification are previously determined recording of input and output values and then after processing these experimental data it is acquired the mathematical model of the phisical system.The 2 approaches does not exclude each other, are complementary in the meaning that:- The mathematical modelling is compulsory when the physical system is not available for an experimental investigation and is just in the form of project- Experimental identification is more precise than analitic modelling but implies the existence of the phisical system and performing an experiment with it

The identification on the base of experimental data of the parameters of the mathematical model imply four stages acquire input output data, chose the model structure,estimate the parameters of the model, validate the identified model (validate structure and value of parameters)The mathematical models obtained as a result of identification allow the study of the systems stabilit. The study of the stability of automatic electrohydraulic systems may be realized on the base of the algebric criteria Routh Hurwity which offers only a condition of stability or on the base of the Nyquist criterium which allows the study of the stability stores. The transfer spot of the system in open circuit has the aspect from fig. 5.

The transfer spot (Nyquist contour) of the servomechanism.

3. Electrohydraulic servomechanismsElectrohydraulic servomechanisms are automatic systems for regulating position speed acceleration or force. The input parameter of the servomechanism is represented by an electric control signal and the output is represented by position speed or acceleration of the rod of the linear hydraulic motor.The components of the electrohydraulic servomechanism are:- the element of comparison- The electronic amplifier- The electrohydraulic amplifier (convertor) servovalve- the operational element the hydraulic motor

51

No.3 / October 2010

The transducer of position speed acceleration or forceThese may be structured in 2 basic subsystems a hydraulic subsystem a drive system and an electronic system of control. The scheme of an electrohydraulic mechanism with electric reaction is shown in fig.6

3.1. The structural and functional description of the test standThe test stand used is a system of automatic regulation an electro servomechanism with electric reaction of position. The automatic regulation implies to bring a physical parameter at a certain value and maintain it at this value This parameter is called regulated parameter. In a process of automatic regulation the regulated parameter is continously measured and compared with the desired value.The automatic regulation must bring a certain physical parameter at a prescribed value and maintain it at this value. This physical parameter is called regulated parameter. In a process of automatic regulation the regulated parameter is continuously measured and compared with the prescribed value.

Fig. 6. Scheme of the test stand1. adjustable volumetric pump; 2.electric motor;

3.normally shut valve; 4. Servovalve; 5-6. pressure transducer; 7. Linear hydraulic motor; 8.

Inductive displacement transducer; 9. inertial mass; 10. Force transducer; 11. Data

acquisition and processing system.

As soon as it is found a difference between these 2 parameters is made an adequate rectification in the installation to be regulated, rectification which must put in accordance the regulated value with the prescribed value.

For the studied system the prescribed value and its comparison with the regulated value and the rectification of the error signal is performed by means of the data acquisition and processing system. This is in fact an industrial computer PXI from National Instruments led by an application LabVIEW realized by the scientists involved in this study.The servomechanism used during the present scientific work comprises:

Hydraulic subsystemSupply unit with oil under pressureAdjustable volumetric pump pos.1Electric motor pos.2Normally shut valve pos.3Servovalve pos.4Linear hydraulic motor pos.7Electronic control subsystemData acquisition and processing system pos.11Pressure transducers pos.5 6Displacement transducer pos.8Force transducer pos.10The technical data of the studied systemLinear hydraulic motorType cylinder with bilateral rodThe cylinder diameter 150 mmRod diameter 70 mmOperastional stroke 160Operational pressure 250 barServovalveType MOOG series 760Pressure 70 barsNominal diameter 6 mmMax flow 40 l/minThe numeric calculus device compensatorConvertor AD 32 channelsConvertor DA 4 channelsResolution AD 16 bztesResolution DA 16 bytesMax sampling speed on AD channels 1.25 MS/sMax sampling speed on DA channels 4.86 MS/sI/O digital 48Software Microsoft Windows XP Lab ViewPeriod of numeric integration 10 ms

52

No.3 / October 2010

Test rig

3.2. Mathematical modellingThe equations which describe the dynamic behavior of the servomechanisms which are of the same type with the one studied in this paper are:- The function of transfer of the servovalve (1)- The equation of continuity specific for the s u b a s s e m b l y s e r v o v a l v e c y l i n d e r servomechanism (2)- Equation of dynamic balance of the hydraulic linear motor (3)

12)(

)()(

2

2

++

=D

D=

ss

K

si

szsH

nn

izSV

w

z

w

ïï

î

ïï

í

ì

£

--

-

=++

0

0

2

|| ; 0

);||

|(|

zz

Ppzsigz

zcb

PR

APkyA s

ddd

h

p

lppr

&&

2

0

12 ph ARJ

e=

sarcinafpp FFPAym --=&&

k – amplifier current –position servovalve slide;iz

(3)

(1)

(2)

where:

nw - natural pulsation of the valve;

z - factor of dynamic amortization

db

ddc

- perimeter of flow through the servovalve distributor;- coefficient of flow of the distribution slopes;

pA

lpk

- active aria of the piston of the hydraulic cylinder;

- coefficient of leaks between the cylinder chambers;

yyy &&&,, - position, speed and acceleration of the rod of the hydraulic motor

P – pressure drop on the couplings of the hydraulic motor;

hR

le

- hydraulic rigidity equivalent on the track

servovalve hydraulic motor;- equivalent elasticity module of the hydraulic oil

z – position of the distribution slide of the servovalve;

0z

sP

- hydraulic coverage of the servovalve;

- pressure of the oil source;r

pm

fF - friction force

- mass of the driven mobile part;

- oil density;

3.3 Selection of operational parametersThe system parameters which may influence the behavior of the studied servomechanism are:- amplitude, type and frequency of the drive signal;- coefficient of proportionality (kp) of the electronic compensator;- inertial mass placed in the upper edge of the rod of the hydraulic linear motor;

3.4. Acquired resultsAt performing the tests was pursued to acquire information regarding the index answer and the answer in frequency of the system. The index answer is shown in fig.7 In fig.9…11 are shown the variations of the parameters pressure in the chambers of the hydraulic lenary motor recorded force with the transducer placed between the rod of the hydraulic cylinder and the load and the drive current of the servovalve for a rectangular drive signal.

The numerical values and the parameter levels are shown in table 1.

Table 1.

53

No.3 / October 2010

In fig.12 is shown the displacement of the rod of the hydraulic cylinder for sinusoidal drive signals with constant amplitude and variable frequency.

Fig..7. Displacement of the piston rod for prompts of 25,50,75,100% from max amplitude

Fig..8. Influence of the compensator amplifier Kp (1; 5; 10)

Fig.9. Pressure Evolution in the chambers of the hydraulic cylinder

Fig. 10. Evolution of the inertial force (M=19 kg)

Fig. 11. Evolution of the drive current through the amplifier

Bode diagram shown in fig.13 was drawn by means of the application shown in fig.14 module of identification of the answer in frequency.

54

No.3 / October 2010

Fig. 12. System answer at a sinusoidal drive signal with constant amplitude and variable

frequency for various values of the coefficient kp = 0.1(a); kp = 1(b); kp = 5(c).

(a)

(b)

Fig. 13. Bode diagram (pt. M = 0; 19; 41 kg ; kp=1)

Fig. 14. Snapshot software interface used for drawing Bode diagram

4. ConclusionsThe experimental results acquired show that there is a very long answering time of the servomechanism. For a drive signal corresponding to a displacement of 100% from the max. value of displacement of the hydraulic cylinder rod, the time constant value is of 1,55 s, for a drive signal of 75% is of 1.4 s for 50% is 1.25 s and for 25% from the entire max value of the prompt the value was of 1.15 s The identified mathematical models were extracted under the form of transfer functions of 1st order for the following operational modes: amplitude drive signal 25,50,75 and 100% of the nominal value. The numerical values of the coefficients are shown in table 2 and show a proper correlation with the index answer.

Tab.2.

Studying the answer in frequency it may be noticed that the system is slow, the cutting frequency being around the value of 0.28 Hz.The difference of phase of the regulation parameters comparing it with the drive value is in this case of 45o. The inertial mass did not have a significant impact upon the answer, which means that the values used were under dimensioned.

55

No.3 / October 2010

An obvious impact upon the index answer was that of the modification of the proportionality coefficient of the compensator, kp. The rise of its value in the interval 1.10 led to the decrease of the time of stabilization of the system but also to the occurence of an over regulation of 2% for a value kp ' 10. A kp value over 12 leads to a slighter amortization of the oscillations so that at a value of 20 the system enters in instability mode (provoked oscillations) The rise of the kp value led to the operation in imbued mode of the servovalve, completely open or shut for sinusoidal drive signals.For continuing the research studies presented above the authors of the article intend to develop a module for determining parameters of regulation of the electrohydraulic servomechanisms by imposing the dynamic performance requirements.The use of the virtual instrumentary allows the fast acquirement of the information of interest regarding the dynamic of the hydraulic regulation systems, the automation of the study process and the optimization of the processes on the groundwork of the performance criteria required. The integration of these technologies of data measurement and processing in the laboratories of hydraulics and pneumatics creates the propitious conditions for the development of the concept of Digital Laboratories.

References1. Drumea, P., Blejan, M., Marin, A., et al. – Virtual instrument designed for dynamic tests of electro-hydraulic devices – 30th International spring seminar on electronics technology – ISSE 2007, 2007.2. Alexandru MARIN, Petrin DRUMEA, The dynamic experimental identification of an electrohydraulic servomechanism National Conference of virtual technology Bucuresti, 2006.3. Anisia-Luiza Gogu, Signals, Circuits and Systems, course notes 2008-2009.

4. Călinoiu, C., Vasiliu N., Vasiliu D., Catană I., Modelling, simulation and experimental i d e n t i f i c a t i o n o f t h e h y d r a u l i c mechanismsTechnical Publishing house Bucharest, 1998.

56

No.3 / October 2010

RECIRCULATION OF POWER AT ENDURANCE AND RELIABILITY STANDS

Ph. student Eng.Radu Radoi*, eng.Mirela Tudor*, eng.I.Balan*

* Hydraulics & Pneumatics Research Institute INOE 2000 - Ihp, Bucharest - ROMANIA

The endurance and reliability stands are high energy consumers, the tests performed on the stand taking a long time. The test becomes extremely expensive when the powers to be developed are high.The diagram for testing parts with rotation motion – pumps and motors – on endurance and reliability stands is well known in the specialized literature. Fig.1

Fig.1 operational diagram for endurance stand

hydraulic pumps and motors with power

recirculation

The object whose endurance is tested is the motor M or the pump P cpupled rigidly. The revolutions n of the 2 units P and M may be equal or different this depending on the type of coupling C (direct or by means of a toothed wheel) The flow discharged by pump P may be entirely discharged into the motor M or the amount is divided between the motor M and tank passing through the valve SP The first situation represents the most advantageous ideal case in which is recirculated the biggest amount of energy. If the entrainment revolutions of the 2 units are equal their displacement must be at least in the relation:

where V – pump displacementP

V – motor displacement M

η – volumetric output of the pump VP

η – volumetric output of the motorVM

Supposing that η = η = 0,95, it results a VP VM

relation = 1,1.

The relation between the power effectively

consumed by the electric motor N and the E

theoretical power transmitted by the hydraulic

motor N will be in this situation:tM

Assuming that it results a relation = 0,33 meaning a recirculation of

67% from the power delivered at the pump outletIn reality it happens that >1,1 and a part of

the flow repressed by the pump to be discharged in the tank at a pressure regulated from valve SP. The power recirculation will be below 67%.Below is presented the principle of recirculating power when performing endurance and reliability tests for hydraulic cylinders.

In fig.2 is shown a diagram of a stand without power recirculation

57

Fig.2 diagram of a stand for testing the endurance

of hydraulic cylinders

The endurance performed on a stand like this implies high energetic consumptions and big installations for cooling oil and for supplying with oil the entrained cylinder.In fig.3 is presented the operational diagram for a stand for testing the endurance of hydraulic cylinders with power recirculation

Fig.3 operational diagram of a stand for testing the

endurance of hydraulic cylinders with power

recirculation

As it may be seen on the leftside we have the same assembly like in fig.1 in the upper part we have 2 identical coaxial cylinders, coupled directly, both being subject to endurance tests. On the rightside is presented the assembly of supply with oil of the entrained cylinder Power recirculation is made by directing the flow bounced by the cylinder entrained towards the recirculation motor M. The flow bounced by the cylinder entrained –rightside- is identical with the flow delivered by the pump P to the entraining cylinder –leftside- the volumetric losses in the 2 cylinders being practically null.It is still valid the condition that the entrainment revolutions of the pump and motor to be equal and their displacement to be approximately equal but always

The overall power result of this installation is the following:

Where N – power consumed by the electric E

motor

N – power transmitted by the pumpP

N – power consumed by the tested C

cylinder

N – power transmitted by the hydraulic M

motor

where: p – operational pressure in the

system (manometer M )2

N – entrainment revolution of the pump

(motor)

V – pump displacementP

η – overall output of the pumptP

where η – volumetric output of the pump VP

η – overall output of the tested tC

cylinder

58

No.3 / October 2010

where: V – the displacement of the hydraulic P

motor

η – overall output of the tested motortM

We have therefore:

Giving common factor in the rightside on

we obtain:

theoretical power transmitted by the hydraulic motor.

Taking into account the condition

(condition for max power

recovery) it results:

The first 2 terms from the rightside brackets represent the power relationship

from the endurance stand of the rotary units with power recovery – assuming the same outputs for pump and motor and a n overall output of the cylinder η = 0,9, we obtain: tC

= 0,43 – a recirculation of power of max. 57%.

Observations:

1. When designing the stand it has to be taken

into account the condition that in the

reciprocate motion of the cylinders never be

reached the stroke end and the change of

positions of the distributor DN to be made

through a field with discharge at the tank of the

pump for not exceeding the power calculated

for the electric motor during commutation or in

stationary status 2. In the presented calculus were not taken into account the losses of power through pipes

Bibliography:

[1].Hydraulic and pneumatic drives vol.1

N.Vasiliu D.Vasiliu

59

No.3 / October 2010

ISSUES RELATING TO THE METHODOLOGY OF ESTABLISHING THE WATER IRRIGATION NEEDS

(1) Constantin NICOLESCU, Gheorghe ŞOVĂIALĂ

(1) National Institue of Optoelectronics Reserch and Development _ INOE 2000, Branch Institute of Hydraulics and Pneumatics Reserch (IHP) Bucharest,

cons_nicolescu@yahoo.com

Abstract:Article deals with 5 methodological aspects of determining irigation water requrements of crops that make the subject of specialized tehnical instructions (ID.1.1985):-monthly balance equation;-equation for monthly net nor calculation;-watering aplication coefficient (rate);-climate deficit relationship;-aridity index;Irrigation works are natural-engineering works for environmental protection

Keywords: Irrigation water requirements, climate deficit, aridity index.

1. Introduction

The calculation method presented in the paper determine the water requirement of plants. Tehnical instructions regarding the methodology for determinig irrigation water requirements of crops are ID.1.1985. These serve for sizing the irrigation arrangement.

I r r i ga t ion works a re na tu ra l -engineering works for environmental protection

2. Material and method

The method adopted for calculating the water requirements of crops is the soil water balance mehod. Soil water balance and irrigation norms calculations should be performed on a series of at least 25 consecutive years.

Soil water balance, to determine water requirements of irrigated crops is calculated over a period of a month.

By calculating the soil water balance, it determine the quantities of water that should be given through irrigation, so that in the vegetation period, the amount of water in the soil will not fall below a minimum threshold called the minimum permissible value. P .(Figure 1) min

where: CC - field water capacity;CO - wilting soil coefficient

CC,CO - expressed as a percentage of soil dry weight

3. Results

3.1. The equation for calculating net monthly balance is shown below:

3(m /ha) (1)

60

No.3 / October 2010

where:

3 ( ) is the amount of rainfail, (m /ha);

- net monthly norm, that actually enters 3in the irrigation system, (m /ha);

- variation of soil moisture reserves for 3the reference periods (decade, month), (m /ha).

ETR0

åp - Ml

RD

3- net monthly consumption, (m /ha) ;

where: 3- final reserve of ground water, (m /ha);

3 - initial soil water reserves, (m /ha).

RR

f

i

3.2.Relationship for monthly net norm calculation

3(m /ha);

/ ETR = d represents a specific coefficient o s

for each textulare category of soil, which shows how covers the monthly net consumption of culture, (%).The d coefficient is obtained from experimental s

research carried out on representative sites.

(2)

(3)

(4)

(5)

where: ETP - potential evapotranspiration - is the total amount of water lost to the atmosphere from the surface of cultivated plots, in full development, provided with plenty of water; d culture-specific coefficient, obtained c -

on the research fields, which is a ETP correction; d = ETR / ETP; c o

d coefficients depend on seeding, the c

length of vegetation, climate conditions, the pace of development of culture, tehnological regime (frequency of watering), uniformity of plant height, soil fertility, coverage of the soil.

3.3. Application factor of watering under experimental conditions

where:

3 - gross irrigation norm; (m /ha)

- watering efficiency

MMl

h

0l

u

3 - net irrigation norm; (m /ha)

(6)

(7)

3.4. Climate deficit

å-=D pETP3(m /ha); (8)

is the climate deficit to ensure the calculation for the month with maximum consumption (July).

(9)

(10)

(11)

k- aridity index

3.5. Aridity index (k) is determine with relationships:

(12)

(13)

(14)

α is calculated for each month and year

61

No.3 / October 2010

4. Conclusions- Tehn i ca l ins t ruc t i ons on t he methodology for determining irrigation water requirements of crops (ID 1 1985) were developed based on research conducted in experimental fields stationary on a series of 10-15 years.- Minimum of experimental data string is 10 years.- This calculation method is applied to the development of technical documentation for irrigation facilities.

Bibliography

1) Mureşan D. şi colab. - „Irigaţii, desecări şi combaterea eroziunii solului ”, Editura didactică şi pedagogică, Bucureşti, 1992.2) Manole Emilia - „Soluţii de reabilitare a sistemelor de irigaţii ”, Editura Nouă, ISBN 978-973-8987-63-0, 158 p. 3) Grumeza N. şi colab. - „Cercetări privind randamentul reţelei de transport şi distribuţia apei în sistemul de irigaţie ”, Analele ICITID, vol. IV, Bucureşti.

62

No.3 / October 2010

NATURAL VENTILATION INDUCED BY SOLAR AIR COLLECTORS

1 2Adrian CIOCANEA , Sanda BUDEA1 Assoc. Profesor, University Politehnica Bucharest, Department of Hydraulics.2 Lecturer, University Politehnica Bucharest, Department of Hydraulics.

Abstract The paper presents three computational models for calculating natural ventilation of a

volume taking into account the internal thermal pressure, the influence of external air currents and the heat transfer inside a solar collector located on the roof of the building. Analyzing the three methods one can observe that the most difficult to assess is the one considering the external wind effect due to its random characteristic. In order to verify the most appropriate mathematical model of ventilation a flat solar collector was calculated for a given building volume. For certain values of the solar radiation total efficiency and air velocities throughout the collector one can observe that two of the mathematical models can be mutually verified. Therefore dimensioning the solar air collector using the first method and then verifying air velocity value with the second method, both dimensions and functional parameters of the flat solar collector are verified.

Keywords (Style “Keywords”): natural ventilation, solar air collectors, heat transfer

Introduction

Heating, cooling and air conditioning in closed areas represents a complex issue that was approached in the long run from studies on air mass moving, air quality aspects, to the energetic efficiency of the buildings, and in the present time, to the public health impact. In this context, the natural ventilation to heating or cooling the areas by using the solar energy and wind contribution represents an actual concern. Studies concerning ventilation process requires solutions to minimize the heating transfer through the building structure in summer time, and respectively using all the internal and external heat sources in wintertime. These processes are in principal connected by two aspects: the convective and conductive heat transfer, respectively heat transfer by radiation –generic named „chimney effect”- and by pressure variations due to the outside air flowing – „wind effect”. Studies regarding the building ventilation have important experimental components, both the chimney effect, also the wind effect don't can be modelling only analytical.

So, many researches was orientates to the chimney effect study, other to the sun azimuth and the angle of solar collector [1] [2] [3] [4] or researches regarding the effects efficiency on the buildings with linear facade [5] [6] 7]. An other researcher category was referred to the technical solutions adoptee to the inclined roofs, by using doubles walls and their forced ventilation [8] [9] [10], or natural ventilation [11] [12], both by combined chimney effect and using solar air heating collectors, [13] also by ventilation systems for all the building with doubles vertical walls, chimney effect [14] and solar collectors [12].The research results have partial generally character because the used dates were attached of special placements. It can obtain same conclusions like the use of solar air collectors are efficient if they are located on inclined roofs [1], [2] and regarding the thermal transfer phenomenon the isolated roof (to reduce the convection and the conduction phenomenon's) must be supplemented by a ventilation channel between the exposed layer and the internal one (double layer roof) to reduce the radiation effect [8].

63

No.3 / October 2010

0So, for inclination of the roof of 30 , the sealing is better and in the space under the roof a reduced flux of the internal heat with approximately 40-50

2 W/m can be obtained. Also, the chimney effect for little height buildings is efficient if these have double walls oriented to south [4] and the natural ventilate roofs have an efficiency with 10% higher if they have double pass [11]. When the angle of the roof inclination is the same with the cell profile for the air flowing, the sealing efficiency increases. [12].In summers the temperature on the roof of the

0 building can reach to max. 75-80 C, function of the inclination roof's and the orientation of the building. On the other side, air flowing can exist around the building that improves the natural ventilation making a negative pressure effect at the building top. These two phenomenons are analysed in this paper that propose also a simplified model of computation to dimensioning a solar air collector to improve the efficiency of the natural ventilation.

I. Computation models for natural ventilation

The mathematical approach of the natural ventilation is made depending of the configuration of the studied building – passive approach – and of the available use of renewable energies – active approach. Also, computation models based only on the thermal pressure inside the building can be used [15] possibly considering the outside air flowing [16] or using the vertical solar air collector mounted on the building facades or on the inclined roofs to induce the air motion from inside to outside the area.

Ventilation using the thermal pressure effect

In simplified model, conform figure 1, the external fresh air with temperature t and 0

pressure p enters from the windows in section 0

1-1 and heat air (polluted) goes out by holes from the bay (scuttle), in section 2-2.

Figure 1. Hall with entering windows on one level

The thermal pressure, that gives the vertical movement H of the mass of the air, with the temperature t and the density ρ in the inlet 1 1

section and the temperature t and the density ρ 2 2

in the outlet section, is give by the relation: p = (ρ - ρ ) g H. (1)t 1 2

By neglecting in a first approximation the wind velocity v, it consider that the air come in by the windows 1, due to the pressure difference:

Δp = p – p , (2)1 0 1

with p the atmospheric pressure. This 0

difference of pressure creates an air movement by the enter holes with a velocity w1

(3)

respectively:

(3’)

with µ = 0,2 ……. 0,65 the flow rate coefficient 1

corresponding to the shape inlet.

By heating the air is lifting and is evacuated by windows 2 due to the pressure difference:

Δp = p – p , (4)2 2 0

Where the pressure p at outlet sections 2 is 2

greater than the pressure in section 1 with the value of the thermal pressure:

p = p +p =p + (r1 - r2) g H, (5)2 1 t 1

and the pressure difference that realise the air outlet conform the relations (4) and (2) is: Dp = (r1 - r2) g H - Dp . (6)2 1

64

No.3 / October 2010

The pressure difference Δp induce an air 2

velocity w flowing through sections 2 and 2

volumetric flow rate and the mass flow rate will be:

relatively of the prevalent wind direction, it can write also the heat thermal transfer as:

r1 c q(t -t ) = Q. (13)p 1 2

The pressures p and p are dynamical I 2

pressures relatively at wind velocity at the upstream and downstream of the building walls, like:

respectively:

(7)

(14)

and with an internal isobar heating:

(15)

using the relations (11)-(14), a mass flow rate results as:

(16)

with plus sign is in the velocity wind direction v and the pressure difference is: Dp = p -p , w 1 2

for A = A =A; 1 2

c = c . d1,2 d

The relation (16) represents a solution of the flow rate equation, knowing the wind velocity, that reality it is not possible to anticipate. Even in these conditions, in a ventilation system the wind contribution can be an advantage if, function of the air streams parameters (direction, sense, intensity, etc.) will be modified the slots from section 2-2 (using adjustable shutters) to obtain a greater air rarefaction than that obtained by only the thermal pressure effect.

The ventilation model using solar air collectors

Considering only the thermal pressure effect and the external wind contribution, it can observe that the natural ventilation of a building is not efficient realises due to its compartments (with important head losses) also due to the impossibility to external wind / air streams prediction.

So, using the solar air collectors to induce supplementary natural ventilation is an efficient solution. In this case the mathematical model estimate the airflow rate through the solar inclined collector with a heat-absorbed material. To specify the solar chimney performances so created, it is considered the heat transfer by solar convection. The main parameters are: the absorbed material temperature and the g lass sur face temperature, the inlet and outlet air temperatures, the environment temperature, the flow rate and openings surfaces.

The mathematical model consist in thermal balance equations at the passing of the solar radiation through the glass cover, heat transfer for the air between the glass cover and the absorbed material and that for the absorbed material in this hypothesis: laminar flow in the air channel; one dimensional processes; parallel geometry for the air channel; the air inlet temperature equal with the environment temperature; head losses neglected; the thermo-physical features are considered for an average temperature.

With the above hypothesis the energetic balance equations for these three elements of the solar collector can be write [12]:

Energetic balance equation for the glass cover

(17)

with:S – solar radiation heat flux absorbed by the 1

2glass cover (W/m )2A – the glass surface (m )g

h – irradiative heat transfer coefficient rwg2between glass and air channel (W/m K)

2A – the collector surface (the wall) (m )w

T – the collector temperature (K)w

T – mean glass temperature (K)g

65

No.3 / October 2010

h – convective heat transfer between the glass g2cover and the air channel (W/m K)

T – the air channel temperature (K)f

U – overall heat transfer coefficient from top of t2glass cover (W/m K)

T – the environment temperature (K)a

Energy balance equation for air, between the absorber material and the glass cover:

The air velocity in the channel can be calculate with the relation:

(18)

(19)

With: Q – heat transferred to the air stream 2(W/m )

m – mass flow rate (kg/s)C –specific heat of air (J/kgK)f1

T – inlet air temperature in air channel (K)fi

T – outlet air temperature from the channel (K)f0

γ – coefficient to approximate the mean temperature (0.74)

The mean air temperature is simplified by:

(20)

So, the equation for the heat transfer by the airstream is:

(21)

By substitute the values of Q results:

(22)

Balance equation for the solar collector can be writing as:

(23)

with:S – solar radiation heat flux absorbed by an 2

2inclined collector (W/m )T – room temperature (K)r

2U – overall heat transfer coefficient (W/m K)b2A and A – inlet and outlet sections (m );0 i

C – coefficient of discharge of air channel 0,57 ;d

L – height of the solar collector (m);s

– the angle of the inclined solar collector with the horizontal;

Using the above relations the mass flow rate through the collector for a room with two openings can be calculate with:

(24)

(25)

II. Case study

Analysing the relations (9), (24) one can observe that the mass flow rate for a heat source Q is given by a relation: kf(T ,T ) where k 1 2

is a constant depending of the considered example and f(T ,T ) is function of de inlet and 1 2

outlet temperatures. In relation (16) it considering also the wind contribution, but due to the complicated shape, in the case study it was not considered. The relation (9) is considering less certain conditions that (24). For calculations of the flat solar collector dimensions one can use the relation (28) where the solar collector efficiency, airflow rate values (air velocity) are introduced; then the geometric values are introduced in relation (24) where new mass airflow rate value and velocity are calculated. A new iteration is performed and the final dimensions of the collector are obtained. In order to verify the method a solar collector inducing air ventilation was considered on the roof of a building like in figure 2.a, b.

The equation for the energetic balance is:

(26)

(26)

with

The surface of the solar air collector results

(27)

is the efficiency of the solar collector,2S – the solar radiation (W/m ),

2A – surface of the collector (m ), tot

v – the air velocity (m/s).

66

No.3 / October 2010

For given air velocities v, various global solar air collector efficiency values and solar radiations magnitude, the surface of the solar air collector results as in table nr.1. By different combined geometries on the roof in figure 2.a these surfaces can be obtained. In figure 2.b the tracks of the collector pipes for the heat / polluted air that arrive in the solar air collector for its rapid exhaust by increasing the air temperature, was plotted. The air velocity function of the solar radiation was considered in figure 3.

Fig. 3 Dimensions of the solar heat air collector at different solar radiation and air velocity

In order to obtain final dimensions of the solar collector, geometric data are introduced in relation (24) and the new value for the air velocity is calculated: v = 1,35 m/s for the case study. Final dimensions are derived using relation (28) (reduced total area A implies tot

small flow section l, as shown in table nr. 1).

67

No.3 / October 2010

I. Conclusion

The energetic building efficiency requires both a better sealing and exhaust of the polluted air. This can be made by a forced ventilation using fans with different air cleaning equipment, dehumidify, etc, by natural ventilation where possible, or by mixed methods. Present paper offers three computation methods for the natural ventilation, mentioning that the consideration of the external wind velocity is difficult to transpose in a technical model, due to its random feature. It was proposed a simplified method to dimensioning a solar collector inducing a flow air rate and performs natural ventilation inside the building. It was considered that solar air collector efficiency value of (15-25)% is a correct assessment for the computation scheme. It was established that two computation relations for the ventilation could be considered (tacking into account thermal pressure and heat transfer in a solar collector) in order to obtain geometrical dimensions using an iteration method.

REFERENCES

[1] N.K. Bansal, R. Mathur, M.S. Bhandari, Solar chimney for enhanced stack ventilation, Building and Environment 28 (1993) 373–377.[2] Z.D. Chen, P. Bandopadhayay, J. Halldorsson, C. Byrjalsen, P. Heiselberg, Y. Li, An experimental investigation of a solar chimney model with uniform wall heat flux, Building and Environment 38 (2003) 893–906.[3] M.M. Aboulnaga, A roof solar chimney assisted by cooling cavity for natural ventilation in buildings in hot arid climates: energy conservation approach in AL-AIN city, 1998, PII: S0960-1481(98)00090-1. [4] J. Mathur, S. M. Anupma, Summer-performance of inclined roof solar chimney for natural ventilation, Energy and Buildings 38 (2006) 1156–1163[5] Balocco C. A simple model to study ventilated facades energy performance. Energy and Buildings 2002;34(5):469–75.[6] G. Gan, A parametric study of Trombe walls for passive cooling of buildings, Energy and Buildings 27 (1998) 37–43.

[7] N.K. Bansal, R. Mathur, M.S. Bhandari, Solar chimney for enhanced stack ventilation, Building and environment 28 (1993) 373–377.[8] P. C. Chang, C.M.Chiang, C.M. Lai, Development and preliminary evaluation of double roof prototypes incorporating RBS (radiant barrier system), Energy and Buildings 40 (2008) 140–147[ 9 ] Z.D. Chen, P. Bandopadhayay, J. Halldorsson, C. Byrjalsen, P. Heiselberg, Y. Li, An experimental investigation of a solar chimney model with uniform wall heat flux, Building and Environment 38 (7) (2003) 893–906.[10] S. Lee, S. H. Park, M. S. Yeo, K. W.Kim, Building and Environment 44 (2009) 1431–1439 An experimental study on airflow in the cavity of a ventilated roof[11] X.Q. Zhai, Y.J. Dai, R.Z. Wang, Comparison of heating and natural ventilation in a solar house induced by two roof solar collectors, Applied Thermal Engineering 25 (2005) 741–757[12] J. Hirunlabh, S. Wachirapuwadon, N. Pratinthong, J. Khedari, New configurations of a roof solar collector maximizing natural ventilation, Building and Environment 36 (2001) 383–391.[13] M. Sandberg, B. Moshfegh, Ventilated-solar roof airflow and heat transfer investigation, Renewable Energy 15 (1–4) (1998) 287–292.[14] G.S. Barozzi, M.S.E. Imbabi, E. Nobile, A.C.M. Sousa, Physical and numerical modelling of a solar chimney-based ventilation system for buildings, Building and Environment 27 (4) (1992) 433–445.[15] Marieta Grigoriu – Instalatii de conditionare a aerului, Lito, Universitatea Politehnica Bucuresti, 1993.[16] Mihai Exarhu, A.Dragomirescu, M. Schiaua- Introducere in aerodinamica Ventilatiei, Ed Printech, 2006.[17] J. Mathur, S.Mathur, Anupma – Summer-performances of inclined roof solar chimney for natural ventilation, Elsevier, Energy and buildings, 10 January 2006.[18] PNII, CEEX 288-DEPOLURB - Cercetarea si dezvoltarea unor echipamente pentru diminuarea noxelor de esapament din spatiile deschise sau inchise ale aglomerarilor urbane.

68

No.3 / October 2010

[19] Adrian Ciocanea, Andrei Dragomirescu, Sanda Budea - Ventilation solution using cross-flow fans for diminising the level of indoor pollution, Conference CEEX 2008, Brasov 27-29 iulie.[20] Ciocanea Adrian, A. Dragomirescu, S. Budea – „On Using Double Air Curtains for Ventilation of Urban Road Tunnels”, Conference on Modelling Fluid Flow CMFF'09 Budapesta, 9-12 set. 2009, pag.525-532, ISBN 978-963-420-986-7.

69

No.3 / October 2010

No.3 / October 2010

RENEWABLE ENERGY TECHNOLOGIES VS. CLIMATE CHANGE

Conf. Dr.ing. Petre Lucian Seiciu*

Abstract. Recently, climate change has escalated from a remote possibility to a menacing reality, thus threatening the planet Earth and its inhabitants. Renewable energy sources became one of the measures in combating climate change. Today, we can find action plans based on international protocols, governments setting up mandatory renewable energy targets. The paper debates on some climate change issues, and critically examines the role of renewable energy as an encountering measure and solicits consolidated action with major emphasis on awareness raising and higher education.

Key words : Climate change, energy education, global warming, renewable energy technologies.

* POLITEHNICA University BucharestMachine Elements and Tribology Departmentlucian.seiciu@as.info.ro

1. Introduction

During the last 2 decades general public opinion realized that we are running out of time in dealing with the greatest threat to Mother Earth and her inhabitants. Most of the scenarios present fearful consequences as a result of the unsustainable technological and industrial development (such as losing land to rising sea levels, shortages of water due to the drying up of waterways and wetlands, sustained and increasingly more severe draughts, and deterioration of flora and fauna). Although, all of these could be considered exaggerations, continuous exacerbation of natural disastrous phenomenon, determined the development of renewable energy researches.

2. Global Warming and Climate Change

It is already of common knowledge that global warming is tightly linked to the exploitation of fossil fuels. Fossil fuels do not represent an endless source of supply of energy and their continued use, even if they were inexhaustible, is the main source of generating greenhouse gas emissions: now established as the main cause of global warming [4].

The United Nations Conference on Human Environment, held at Stockholm, Sweden in 1972, saw the need to state that “…We see,

around us, growing evidence of manmade harm in many regions of the earth: dangerous levels of pollution in water, air, earth and living beings; major and undesirable disturbances to the ecological balance of the biosphere; destruction and depletion of irreplaceable resources; and gross deficiencies, harmful to the physical, mental and social health of man, in the manmade environment, particularly in the living and working environment.” [5]. This first such conference ever recommended “… that the General Assembly of the United Nations decide to convene a second United Nations Conference on the Human Environment; …” so as to maintain the momentum of the first conference [6]. around us, growing evidence of manmade harm in many regions of the earth: dangerous levels of pollution in water, air, earth and living beings; major and undesirable disturbances to the ecological balance of the biosphere; destruction and depletion of i r rep laceab le resources; and gross deficiencies, harmful to the physical, mental and social health of man, in the manmade environment, particularly in the living and working environment.” [5]. This first such conference ever recommended “… that the General Assembly of the United Nations decide to convene a second United Nations Conference on the Human Environment; …” so as to maintain the momentum of the first conference [6].

70

No.3 / October 2010

Yet, it took 20 long years before this second conference was finally convened [2]: The Earth Summit at Rio de Janeiro, Brazil, in 1992, “unprecedented for a UN conference, in terms of both size and concerns' scope.” [7]. This was followed - 10 years later - by The Earth Summit at Johannesburg which was dubbed Rio+10. The so called Johannesburg Declaration on Sustainable Development, recognized – among other things – that the future belongs to children “…who represent our collective future” and that we – accordingly – have “…a collective responsibility to advance and strengthen the interdependent and mutually reinforcing pillars of sustainable development – economic and social as well as environmental protection – at local, national, regional and global levels.” [8].

Meanwhile, climate change has been advancing unabated, with Australia having its hottest year in 2005 ever since records started to be kept in 1910 [2]. The annual average temperature in 2005 was 1.09°C higher then period average between 1961 and 1969, seen as further verification that our climate is changing [9].

Despite all of these, it has been relatively easy, especially for those deeply immersed in business or politics, to dismiss the warning signs of an impending global crisis. Utterances by scientists have been considered unfounded myths meanwhile scientist were treated as negative forces impeding the growth of economy. Only around middle of the last century concerns were raised regarding the detrimental effects of mindless exploitation on the collective riches of the planet and its inhabitants.

Global warming due to the excessive release of the greenhouse gas emissions in the process of generating heat to facilitate the energy conversion processes is now seen as the root cause of the climate change problems [4].

Climate change become real; it is no longer just a horror scenario dreamt up by a few eccentric scientists as it was thought to be just until very recently. So real that most credible warnings are sounded, alarming that dire consequences are in sight if no action is taken to combat this most real threat to the planet Earth. The awarding of the 2007 Nobel Peace Prize, in December 2007, to the Intergovernmental Panel on Climate Change (IPCC) of the United Nations Organization, jointly with Al Gore, has lent indisputable credibility to the claims that our planet is in dire straits [10].

The problem of climate change is universal and overwhelming. The process toward achieving amicable and sustainable outcomes for all of Earth dwellers in their quest is to find out why all this is happening and how it can be stemmed. Solutions cannot be expected without understanding cause-effect relationships. It is now well established beyond reasonable doubt that climate change is the worst menace that Earth has ever faced [4], [11], [12].

3. HANAR model

It is very difficult to quantify the bi-polar relation between human actions and nature's response due to the immenseness of the parameter involved. Human Activity-Nature Rebound (HANAR) model is proposed in this paper as a simple model to help understand the phenomenon and as a basis for a future mathematical complex model. During the human history (Homo sapiens appeared approximately 12,000 years ago), except last hundred years, the human activities left no visible ecological mark on Earth. The state of facts could be represented as in Fig.1. Human activities h(x) occurring between state 1 and state 2 were compensated by natural rebound n(x) as a planetary proportion feed-back so, climate was not affected by human activity.

Fig. 1. HANAR model for human history minus last

1 2

h(x)

n(x)

x

Fig. 2. HANAR model for the last 50

1¢

h(x)

n(x)

x 1 2

NR(x)

71

No.3 / October 2010

Within the last 100 years and especially in the last 50 years, things have changed (Fig. 2). Human activity could not be compensated by natural rebound (state 1) therefore; non-rebounded zone – NR(x) – appeared. In this figure, the X axis represents various parameters affected by human activity (global temperature, % of toxic gas, % of ozone layer destroyed, excessive agriculture effects, raw material exploitation effects etc.).NR(x) represents, in fact, un-rebounded human activity. Its existence and size will generate the ecological response, the sustainable policies and the development of renewable energy technologies. Of course, the aim is to overlap states 1 and 1, thus NR(x) becoming zero.The total human activity can be written as:

ò=2

1

)( dxxhTh

ò=2

1

)( dxxnRh

The natural rebound effect is defined by:

(1)

(2)

(3)

(4)

The un-rebounded human activity is determined to be:

ò=2

1

)( dxxnNR

A axis diagram is plotted in Fig.3 where: x , x 2 1 1

and x are the parameters ' va lues 2

corresponding to the states 1, 1 and 2, respectively; A , A and A are the human 1 1 2

activities corresponding to states 1, 1 and 2, respectively.The total compensatory activity to be performed in order to eliminate the non-rebounded zone is:

11 AACa -= ¢

Two axis HANAR model is a more explicit representation of the phenomenon, thus more appropriate for a further mathematical approach.

4. Counter Measures

Worldwide, counter measures have been put in place at a frantic pace. Kyoto Protocol [13] arguably represents the most decisive of these measures with its binding commitments to reduction in emissions and renewable energy targets. It legally binds the parties to the Protocol to “…individually or jointly, ensure that their aggregate anthropogenic carbon dioxide equivalent emissions of the greenhouse gases … do not exceed their assigned amounts, calculated pursuant to their quantified emission limitation and reduction commitments … with a view to reducing their overall emissions of such gases by at least 5 per cent below 1990 levels in the commitment period 2008 to 2012.” [13]. Table 1 summarizes the member states' commitments to reduction targets.

TABLE 1 - Greenhouse gas emission targets for 2008-2012(Kyoto Protocol – Annex B) [13]

72

No.3 / October 2010

Bali Mandate, held at Bali in December 2007 further raises the stakes, and - with it - the hope that there may a turn-around before it is too late. Commenting on the complexity of the negotiation, John Connor wrote in The Age Australian newspaper, on December 2007, under the heading “Ducking and weaving along a risky path to a better future”: “After an extraordinary day of global political theatre, about 190 nations hammered out a Bali mandate. The result is a rough and risky road map skirting some dangerous territory, but with some signposts to safety for the future of our planet and our children.” [14].

Signs of an awakening and awareness on the part of governments, businesses, major organizations and the international community can be foreseen. There is interaction, collaboration as evidenced by various agreements. Also, there seemed to be an increased awareness, leading to concerns expressed by groups and individuals everywhere. The counter measures instituted are yet to produce results since the whole world is eagerly anticipating positive outcomes from these initiatives. Not surprisingly, renewable energy in its different guises is touted as a primary element in any of these initiatives.

5. Renewable Energy

Many have come to consider the use of renewable energy sources as the panacea for solving the climate change problems [2].

Renewable energy is variously defined as energy obtained from sources considered inexhaustible such as the sun, wind, waves, tides, bio-fuel and geothermal energy. In remarkably large instances, the use of renewable energy resources remains as being inextricably linked with generating electricity. That is not surprising in view of the fact that electrical engineering, as a genre, has been the most progressive and influential field of engineer ing, dominat ing engineer ing achievements and providing indispensible m e a n s o f e n e r g y u t i l i z a t i o n a n d communication.

Generating electricity using non-renewable sources of energy such as coal and natural gas is one of the major contributors to greenhouse

to find benign sources of renewable energy.

In Australia, the concept of renewable energy is linked to electricity by legislation. There is a government instrumentality, labeled Office of the Renewable Energy Regulator (ORER), which administers the legislation and regulations. ORER's aim is to increase the level of Australia's renewable electricity generation. The target set by the newly elected government is 20% of the total by 2020 [15]. Similar measures are introduced elsewhere.

With reference to the USA, it has been asserted that “renewable energy is a force today and will be a major force in America's future – the only question is when. The answer will depend only on the will of the American people for clean energy – or the next major political disruption in the Middle East.” [16].

In an effort to sustain their lifestyle, objections have been raised from different quarters to switching over to renewable energy. These objections are usually based on higher costs of renewable energy technologies, including life-cycle costs in the case of solar and wind energy solutions. It has also been pointed out that large quantities of non-renewable resources are required to erect large wind generator towers. It has been argued that most renewable energy installations are aesthetically wanting, whether they are solar panels, tidal power plants or wind turbines. Objections have also been raised to the use of biofuel as source of energy arguing that this would alienate valuable land surface from agriculture and forestry, thus possibly leading to high cost and shortages in basic commodities, most notably food. Such dissenting voices challenge the notion that renewable energy is the panacea in thwarting the gauntlet of climate change [2].

6. Future steps

The UN Organization spurred its member states to action and now, most Governments are setting the framework for greenhouse gas reduction, legislating for mandatory reductions in emissions coupled with mandatory targets

gas emissions thus; there is a strong necessity

73

No.3 / October 2010

for renewable energy meanwhile large corporations are investing heavily in renewable energy.

Also, there is renewed interest in renewable energy education and research. Courses dealing with renewable energy issues seem to be popular in university engineering programs at the same time that research into different aspects of renewable energy application attracts increasing interest. Motivation to engage in renewable energy research is driven by a self-preservation instinct as well as by a communal responsibility.

7. Role of Education

Education looms as one of the most important weapons in combating the problems of climate. There are many initiatives taken around the globe that vary from programs at elementary levels of schooling to professional engineering degree programs at university level [18] [19].

The role of education in the contemporary framework of world events has to be appreciated through the nature of the problems to be faced: universal, indiscriminate, and overwhelming problems! Humankind is grappling with the almost impossible task of finding solutions to problems beyond its collective comprehension. Parochial interests hamper progress in reaching agreements. Hence, the contemporary education has to break through parochial boundaries of national interest, inculcating the importance of selfless cooperation within the global community for common good. Such pr inc ip les were a r t i cu la ted under Recommendation 96 of the 1972 United Nations Conference on the Human Environment, held in Stockholm, namely: “It is recommended that the Secretary-General, the organizations of the United Nations system, especially the United Nations Educational, Scientific and Cultural Organization, and the other international agencies concerned, should, after consultation and agreement, take the necessary steps to establish an international program in environmental education, interdisciplinary approach, in

school and out of school, encompassing all levels of education and directed towards the general public, in particular the ordinary citizen living in rural and urban areas, youth and adult alike, with a view to educating him as to the simple steps he might take, within his means, to manage and control his environment.” [20].

Fig. 4. Splendor of Rainforest as vividly depicted by Senaka Senanayake

As the members of the generation which has been slumbering while the climate change has been sneaking on us, we have the onerous responsibility to reach out in educating everyone we can possibly touch. Says Senaka Senanayake – the world renowned Sri Lankan artists, whose paintings adore the United Nations Building in New York and White House in Washington D.C.: “I am quite moved by the environmental crisis and I try to use my skills to attract people to understand and enjoy the beauty of the rain forest. When they become aware they will begin to understand the crisis.” [21]. He focuses on young children, visiting schools, talking to them, showing them his brilliant paintings of the rain forest: plants, flowers, leaves, birds, butterflies. He wants them to see and understand how beautiful the things are that they are about to lose, hoping to arouse passion so that they may become the new guardians of our precious heritage.

Education is a key ingredient in the fight against global warming and everything else it stands for: education at all levels – from the layman in a country property to the research scholar at a research institution. All need to see how precious the things are that we may be about to lose, and join the fight to save them.

74

No.3 / October 2010

8. Renewable Energy Education & Research

Motivation and passion are sorely needed once one becomes aware of the magnitude of the problems that the humankind is facing. But, motivation and passion are no substitute for skill. Ultimately, sympathetic solutions can only be provided by people who are specifically educated to develop skills to implement renewable energy solutions. This applies in particular to engineering and allied disciplines.

Fig. 5. Santa Clara University assembling their solarhouse on campus in preparation for 3rd Solar Decathlon

Fig. 6. Kansas State University and University of Kansas “show and tell” about use of structural insulated panels

To motivate, to arouse passion for the responsibilities ahead, engineering educators and research supervisors themselves need to be motivated and be passionate about what they are teaching or directing. Following are two examples from opposite sides of the world which may provide some inspiration. Both examples require qualities such as motivation, persistence, dedication, enthusiasm, skill and willingness to learn more skills in a congenial team environment.

A. Solar Decathlon

Solar Decathlon is a competition, primarily supported the U.S. Department of Energy (DOE), in which teams of university students design, build and demonstrate an attractive solar house of average size [22]. The emphasis is on the sole use of solar energy to provide for all energy needs of the dwelling including electricity, whilst doing it efficiently and attractively. Inaugurated in 2001, it has been held in 2005, 2007 and 2009, the fifth event scheduled to be held in 2011. DOE has recently released the names of 20 teams selected to compete in 2011 Solar Decathlon. The press release also announced that “... each team will receive $100,000 from DOE to uniquely design, build and operate an energy efficient, fully solar-powered home for this unique competition.” [23].

DOE purpose is to “…challenge student competitors to think in new ways about energy and how it impacts our everyday lives, to provide those students with a way to show and tell the world what they have learned, to push research and development of energy efficiency and energy production technologies and to encourage all of us to act responsibly when making energy choices.” [24]. The competition's name – Solar Decathlon – reflects on the ten different contests, by which each entry is judged: archi tecture, engineering, market viability, communications, comfort, appliances, hot water, lighting, energy balance and transportat ion. Transportation is included as a requirement for providing sufficient electrical energy to charge an electrical commuter vehicle. The teams have some 18 months to analyze, research, design, redesign and build their solar house. Construction is undertaken on the university campus, as depicted in Fig. 5.

75

No.3 / October 2010

Once completed and commissioned, the house is dismantled and transported to the National Mall, Washington D.C., for reassembling in a solar village. Public is invited to come and see the latest-under-the-sun! Teams enthusiastically share their knowledge and experiences with the visitors as recorded in Fig. 6.

The Solar Decathlon educates, demonstrates and offers fresh hope by giving evidence that it can be done.

B. World Solar Challenge

World Solar Challenge is a race across the continent of Australia from Darwin in the north to Adelaide in the south, covering a distance of just over 3000 km [25]. Its purpose is to promote research into zero emission trans-port solutions. As the name implies, solar energy is the sole source of energy for use during the race.

In 1997, the South Australian Solar Car Consortium was formed upon the initiative of the University of South Australia (UniSA). The consortium included UniSA and three local high schools and its aim was to motivate students to take up engineering as their study path upon completing high school, in addition to raising their level of awareness of environmental issues. This was to be achieved by helping design and build a real solar car for real people

Fig.7. Solar car designed and built by the South Australian Solar Car Consortium

Fig. 8. Two-seater renewable energy vehicle: TREV, designed and built at the University of South Australia

for was to be the World Solar Challenge. The first solar car, nicknamed “Ned” after Australia's most infamous folk hero Ned Kelly, was designed and built under the supervision of academics, which infused their enthusiasm in the students working as composite teams (Fig. 7). These comprised university students from various engineering disciplines and high school pupils. Ned made its debut at the 1999 World

th Solar Challenge, coming first in its class and 14overall.

In 2000, Regency TAFE, a college of technical and further education joined the consortium. Soon, the Consortium was working on Kelly, the next generation solar car.

Meanwhile, UniSA team had accepted the challenge of designing and building an ultra-efficient, low-mass electric vehicle powered entirely by renewable energy. Thus, work started on TREV: Two-seater Renewable Energy Vehicle (Fig. 8).

TREV's features have included sufficient room for modest luggage, energy efficient tires, brakes and suspension, a quiet and efficient electrical drive and compliance with road safety regulations and road worthiness requirements. TREV weighs 300kg and has a driving range of 150km before recharging. Its energy consumption is about 20% of a comparable passenger vehicle.

76

No.3 / October 2010

It can accelerate, smoothly and quietly, from standstill to 100km/h in less than 10 seconds. The tandem seating arrangement results in good stability and visibility. The single rear drive wheel simplifies the suspension, and allows a simple, efficient transmission. It has an ae rodynamica l l y des igned and aesthetically pleasing body with a transparent canopy. Both the canopy and the door open on the curbside for safe access. Completing the race in just over 6 days with an energy consumption of 6.2kWh/100km [26], TREV was successfully entered in the 2007 World Solar- Challenge in the Green fleet Technology Class.

8. Conclusion

It is now beyond question and of overwhelming evidence that our planet becomes unfit to sustain life.

There are compelling reasons for humankind to embrace any measure offers a glimmer of hope to deviate from the perilous course that we are on without having counted the cost in the first place.

Engineers carry a special responsibility on account of their knowledge and skills in dealing with issues arising from the conversion and use of energy. This behaves us to take a lead and be actively involved in matters pertaining to climate change and renewable energy.

It isn't late to hope that we will somehow sail out of troubled waters provided we pull together, rowing on the same boat.

References

[1] W. Paddock, P. Paddock, Famine-1975! America's Decision: Who will survive?, Little, Brown and Co., Boston (1967), 286 pp. [2] Ö. Göl, (2008): Renewable Energy – Panacea for Climate Change, School of Electrical and Information Engineering, University of South Australia, ozdemir.gol@unisa.edu.au, 11/07/2008, 8 pp.

[3] N. Eberstadt, (1995), “Limits of Statistical Certainty: The Case of Population, Food, and Income", in The True State of the Planet, (R. Bailey, ed.), Free Press, New York (1995), pp. 455-459. [4] IPCC, 2007: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment, Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Ave-ryt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 996 pp. [5] United Nations Conference on the Human Environment, 1972, Stockholm, Sweden, http://www.unep.org/Documents.Multilingual/Default.asp?DocumentI D=97&ArticleID=1503&l=en (2008). [6] United Nations Conference on the Human Environment, 1972, Stockholm, Sweden, http://www.unep.org/Documents.Multilingual/Default.asp?Docu mentID=97&ArticleID=1515&l=en (2008). [7] United Nations Conference on Environment and Development (UNCED), Rio de Janeiro, 3-14 June 1992, http://www.un.org/geninfo/bp/enviro.html(2008). [8] Johannesburg Declaration on Sustainable Development,http://www.un.org/esa/sustdev/documents/ WSSD_POI_PD/English/POI_PD.htm (2008). [9] Australian Government Bureau of Meteorology, “Annual Australian Climate Statement 2005”, http://www.bom.gov.au/announcements/media_releases/climate/change/20060104.shtml (2005). [10] Ecologic - Institute for International and E u r o p e a n E n v i r o n m e n t a l P o l i c y , http://www.ecologic.eu/modules.php?name=News&file=article&sid=2238 (2008). [11] R. Pachauri, “Presentation at the Opening Session of the UN High Level Event on Climate Change, New York, 24 September 2007”, http://www.ipcc.ch/graphics/speeches/rajendra-pachauri-september-2007.pdf [12] Z. Yu, Issues on Renewable Energy Development in China, Power Engineering Society G e n e r a l M e e t i n g , 2 0 0 7 , I E E E , D O I 10.1109/PES.2007.386158, pp. 1-6. [13] Kyoto Protocol to the United Nations Framework Convention on Climate Change, http://unfccc.int/resource/docs/convkp/kpeng.html (2008). [14] J. Connor, “Ducking and weaving along a risky path to a better future”, http://www.theage.com.au/ news/climate-watch/ducking-and-weaving-along-a - r i s k y - p a t h - t o - a - b e t t e r -future/2007/12/16/119774009 0794.html (2008).

77

[15] Australian Government – Office of the Renewable Energy Regulator, “Increasing Australia's renewable electricity generation”, http://www.orer.gov.au/legislation/index.html (2008). [16] S. R. Bull, Renewable Energy Today and Tomorrow, Proceedings of the IEEE, Vol. 89, No. 8, August 2001, pp. 1216-1226. [17] K. Malmedal,B. Kroposki, P. K. Sen,Energy Policy Act of 2005 and Its Impact on Renewable Energy Applications in USA, Power Engineering Society General Meeting, 2007, IEEE, DOI 10.1109/PES.2007.386060, pp. 1-8. [18] R. B. Bass, A Bachelor's Degree Program in Renewable Energy Engineering, in Proceedings Frontiers in Education Conference, 36th Annual, 27-31 October 2006, pp. 13-16. [19] B. Hadzi-Kostova, Z. A. Styczynski, Teaching renewable energy using mult imedia, in Proceedings Power Systems Conference, 10-13 October 2004, vol. 2, pp. 843-847.

No.3 / October 2010

[20] United Nations Conference on the Human Environment, 1972, Stockholm, Sweden, http://www.unep.org/Documents.Multilingual/Default.asp?DocumentI D=97&ArticleID=1511&l=en (2008). [21] H. Bhatkal, Senaka, Popular Prakashan, New Delhi (2008), p. 175. [22] U.S. Department of Energy, Solar Decathlon, http://www.solardecathlon.org/ (2008). [23] U.S. Department of Energy, “Energy Department Selects Student Teams to Compete in 2009 Solar Decathlon”, http://www.energy.gov/news/5888.html (2008). [24] U.S. Department of Energy, “Solar Decathlon: Fulfilling a Purpose”,http://www.solardecathlon.org/purpose.html (2008). [25] World Solar Challenge, http://www.wsc.org.au/ (2008). [26] University of South Australia, TREV (two-seater renewable energy vehicle) http://www.unisa.edu.au/solarcar/trev (2009).

78

79

No.3 / October 2010

ELEVATION AND TRANSPORT EQUIPMENT WITH DOUBLE SOURCE OF ENERGY

1 1eng. Florin GEORGESCU eng. Liliana DUMITRESCU 1 phd. eng. Dragoş GUŢĂ 2eng. Laurentiu VEBER

1 – INOE 2000-IHP Bucuresti2 – SC PRESTCOM SA Focşani

Abstract

Most of the actual elevation equipment use the hydraulic power by means of pumps driven manually or

electrically, from a set of batteries. In the last situation, although the operation is more comfortable, is not

always justified economically, mainly in the cases of light and average loads, because of the high price.

Another issue refers to the weight of the lifting equipment.

The solution below addresses to the companies where are lifted and carried light and medium loads, below

1000 kg, and many operations of loads deplacement upwards are made from quasi-stationary positions.

The solution offers an easy alternative to the manual operation commonly used for elevation means.

Keywords: elevator, hydraulic, double, energy

1. IntroductionThe elevation and transport of the load is an operation which is very commonly performed in most fields of activity, in production and related fields. There is a great variety of elevation equipment for diffrent loads in matter of shape, volume and weight.Taking into account the interest in reducing the effort of the manipulators of these elevation and transport means, they were improved, replacing the human energy used for elevation and transport of the loads, with electric energy, stored in batteries.The disadvantages of this solution relate to:

- the heavy weight of the assembly, cause of the accumulators and the elements connected to the electric operation

- the long charging t ime of the accumulators, due to their big volume

- the high price of the final productAlthough, for manipulating light loads, below 1000 daN, which represents a very common activity in the small and medium size companies, it is maintained the manual operation, for both lifting and carrying the loads.If the transport is made several times on short distances and this does not imply any major

physical strain, the elevation implies a significant number of actuations of the pump, situation which becomes tiresome for the operator, being reiterated for so many timesIHP - the Hydraulics and Pneumatics Research Institute developed an elevator for industrial loads which combines the manual operation with the electro hydraulic. The product was created in collaboration with the company SC PRESTCOM SA Focsani during an INOVARE research project, carried on between 2008 20102. The proposed solution structure and operationThe elevator shown in figures 1 and 2 comprises mainly a mechanical elevation sub- assembly (1) which has as active element the hydraulic cylinder (2) supplied by a manual pump (3) - classic elevator -, an electro-hydraulic drive unit (4) and a hydraulic circuit (5) which allows the selection of a certain type of operation, depending on possibilities. The work prompts in the case of the electro hydraulic actuation are made from an electric panel.The two operational modes in which the elevator may work for elevationing loads are:

No.3 / October 2010

- The manual operation mode the elevation of the loads being performed by means of a manual pump and the descent by the manual opening of a tap.

- The electro-hydraulic operation mode at which the elevation of the loads is performedby means of an electro-hydraulic unit in the

Figure 1 - Elevator with double source of energy (physical accomplishment) Figure 2 - Elevator with double source of energy

(operational scheme)

The work in the two operational modes of the elevator is the following:a. Manual operation - the handle lever of the pump (3) is driven, the fluid is absorbed from the common tank (6), passes through the directional valve (7) and reaches the hydraulic cylinder (2). This generates the elevation of the platform on which is placed the load to be lifted, having provided at the head of the rod a chain wheel over which passes a chain fixed at one of the heads by the fix structure of the elevator and the other head being linked to the platform.The use of the mechanism with pulley allows a double stroke of the cylinder at the platform which is useful in the case of manual operation, reducing the number o operations of the pump required for obtaining a certain elevation height.

For descent actioned manually is opened the tap (11) allowing the fluid flow from the cylinder to the reservoir and the descent of the load with a controllable speed.

situation in which exists the possibility of connecting to the public electric network 230 Vac and the deplacement of the loads is made mostly vertically unload load a transport means The descent is also made electrically due to a command given to a hydraulic distributor.

b. Electro hydraulic operational mode - in this case the installation is connected to the public electric supply network From the control panel (6) is supplied the electro-pump (9) formed by an electric motor and a simple gear pump, which is capable to satisfy the requirements in matter of flow and pressure. It is also supplied the electromagnet S of the directional valve with electric drive (10) 1

whose spool goes rightwards allowing the oil flow to the cylinder (2); in this situation the path to the tank (12) is blocked cause of the tap (11) and the directional valve (7) restrains the flow by the manual pump (3).For the descent is actioned from the panel (6) the power supply of the electromagnet S of 2

the directional valve (10) allowing the controlled flow of the oil from the cylinder under the action of the platform loaded or not.

80

No.3 / October 2010

Figure 3 - Hydraulic scheme

3. Main technical featuresThe main features of the elevator are given below.- Maximum deplaced load: 1000 kg- Maximum height: 1600 mm- Number of actions of the pump (manual mode): 58- Average time of elevation in manual mode: 3s/double stroke- Electric power installed 1.5 kW

- Average time of elevation for electro hydraulic operation: 16 s- Voltage: 230 Vac- Total weight: 295 kg

4. Experimenthal resultsElevator has been tested in both types of reg imes , manua l , e lec t ro -hyd rau l i c respectively. Were measured the time for lifting in the two variants and working pressure to lift a 500 kg weight load, half load.Schedules are given below.

Figure 4 – Time to rise to maximum height (1600 mm) and descent, manual version

81

No.3 / October 2010

As shown, the rising operation manual version is a high time, approx. 140 s, and during a double-stroke pump, half the time is intended to return lever hand pump in position and can be regarded as dead time.Lowering in the manual mode is performed in approx. 30 s.

Figure 5 – Time to climb to maximum height (1600 mm),

electro-hydraulic version, and manual lowering

Figure 6 – Time to climb to maximum height (1600 mm),

electro-hydraulic version, and electric lowering

Rising with the electro-hydraulic drive system is performed in a much shorter time than the previous version (approx. 14 s); the lowering through the electric distributor is about 7 s (figure 6), unlike the case of lowering manual mode (30 s - figure 5).

Figure 7 – Working pressure for rising, electro-hydraulic mode

82

No.3 / October 2010

Working pressure is about 75 ... 80 bar and maximum pressure relief valve was set at 125 bar.

5. ConclusionsIn the electro-hydraulic variant, the elevator facilittates the loading and discharging operations, shortening the time of the operation 10 times, and lessening the physical strain of the operator.The descent can be done manually, regardless of how the lifting of the load, so the load can be lifted in electro-hydraulic mode, and can be moved and lowered manually, if there is no available source of electricity.The additional weight added by the electro-hydraulic unit and the other hydraulic components necessary for interconnecting the 2 power sources - the manual pump and the electro-pump - is not very significant, representing some 10% from the entire weight of the equipment.

Bibliography

1. Oprean, A., Ionescu, Fl., Dorin, Al. – Actionãri hidraulice. Elemente si sisteme, Editura Tehnicã, 1982.2. Chirita, C., Calarasu, D. - Actionarea hidraulica a masinilor unelte. Editura PANFILIUS, Iasi, 2002, ISBN 973-85195-2-7.3. Avram, M., - Actionãri Hidraulice si Pneumatice. Echipamente si sisteme clasice si mecatronice.Editura Universitarã, Bucuresti, 2005, ISBN 9737787-40-4.4. Alãmoreanu, M., Tisea, T. – Masini de ridicat, Editura Tehnicã, Bucuresti, 1996- Brochures and catalogs of companies: NIKE Hydraulic, ENERPAC, HAWE, PARKER, HYDRAMOLD- Col lect ion OIL HYDRAULIK UND PNEUMATIK

83

No.3 / October 2010

84

OPTIMISATION OF THE TARGET CONTROL WITH NEURAL NETWORK Adrian Olaru, Aurel Oprean, Machines and Manufacturing Systems Dep. University Politehnica of Bucharest, Bucharest - ROMANIA, e-mail:aolaru_51@yahoo.comSerban Olaru, Mechatronics Department, RomSYS Company, Bucharest, Romania, e-mail: serban1978@yahoo.com Dan Paune, General Manager, S.C.Metal Plast, Bucharest, Romania,e-mail:metalplast@yahoo.com

Abstract: The paper shown one assisted method to construct simple and complex neural network and to simulate on-line them. By on-line simulation of some more important neural simple and complex networks is possible to know what will be the influences of all network parameters like the input data, weight, biases matrix, sensitive functions, closed loops and delay of time. There are shown some important neurons type, transfer functions, weights and biases of neurons, and some complex layers with different type of neurons. By using the proper virtual LabVIEW instrumentation in on-line work, were established some influences of the network parameters to the number of iterations before canceled the mean square error to the target. Numerical simulation used the proper teaching law and proper virtual instrumentation. In the optimization step of the research on used the minimization of the error function between the output and the target and the proper teaching low. The new network type bipolar sigmoid hyperbolic tangent neural network with time delay and recurrent links show was established after assisted research of some known networks, by eliminate the deficiencies of them.

Keywords: sensitive function; neuron; neural network; control system; virtual simulation; LabVIEW instrumentation

I. INTRODUCTION In many applications where were needed

extreme precision, accuracy and stability of the way or of the guidance, the accuracy of taking the image, the accuracy to talk or to here, will be necessary to apply the neural networks.

A first wave of interest in neural networks was the introduction of simplified neurons by McCulloch and Pitts in 1943. These neurons were presented as models of biological neurons and as conceptual components for circuits that could perform computational tasks. Many other application of the neural networks has try to developing this field, most notably were Teuvo Kohonen, Stephen Grossberg, James Anderson and Kunihiko Fukushima [1…10].

Neural network are composed of simple elements operating in parallel, like a biological nervous systems. As in nature, the elements of the neural networks (neurons) are connected between them with the synapses what well balance the information. Thus, the decision will be taken after analyze of the sum of these information from the neurons after was applied the influences of each biases and sensitive functions. You can train a neural network to perform a particular function by adjusting the

value of the connections (weights) between elements. Neural network have been trained to perform complex functions in various fields including pattern recognition, identification, classification, speech, vision and control systems. We consider neural network as an alternative computational scheme rather that anything else. The artificial neural networks which we described in this paper are all variation on parallel distributed processing (PDP) idea. An artificial network consists of a pool of simple processing units which communicate by sending signals to each other a large number of weighted connections, number and sensitive functions what can be changed by using the LabVIEW optimization method shown in this paper. Typically, neural network are adjusted, or trained, so that a particular input leads to specific target output. The network is adjusted, based on comparison of the output and the target, until the network output matches the target. Typically, many such input/target pairs are needed to train a network.

No.3 / October 2010

II. THE MORE IMPORTANT USED SENSITIVE FUNCTIONS The sensitive functions are applied in each neuron types. In a dependence of the target, will be applied one or other of them. To know the action of them will be necessary to simulate them. The most important sensitive functions are presented in fig.1.[10]

Figure 1. Sensitive functions: a) perceptron; b)linear; c) sigmoid unipolar; d) radial

Each of the used sensitive functions determines one general function of the neural layer, such a saturation to 1 of all positive values (fig.1a), the same output like a input (fig.1b), progressive convergence to the 1 or 0, if the inputs are positive or negative, Gauss variation to the 1 value, if the inputs are near 0 value, and s.o. By each type of the sensitive functions, the neurons or the layers involves them like a special filter, amplifier and with the influence of the biases matrix, what assures the translation of the function, can adjusting the field of the output.

III. MATHEMATICAL MODELS OF SOME IMPORTANT COMPLEX NEURAL

NETWORKS The more important neural network and

proper mathematical models used in the recognition the voice, the form, to optimize the guidance trajectory are presented in the figs.2-7[10].

85

No.3 / October 2010

All proper mathematical models assures conditions for the simulation and optimization them with LabVIEW propre virtual instrumentation.

IV. THE NUMERICAL SIMULATION OF THE NEURAL NETWORKSThe numerical simulation of the neural network used one algorithm presented in [11, 12] what

contents the elements specified in fig.8.

Figure 8. The neural network general schema with input LabVIEW data

The input data for the numerical simulation with LabVIEW will be: the number and data of the input vector, the number of neurons for each of the layers, the teaching gain, the sigmoid bipolar gain and the target output data. All matrixes of biases and weights were initialized at 0. To easily obtain the convergence was created one proper method of teaching law, what was applied in the paper. The base of the teaching law is to determine the error between the target and the output in each layer, by the transfer the target to each layer and adjust the

ierror by teaching gain ν . The mathematical equations are:

86

No.3 / October 2010

i i -i where t is the target and a is the output of each layer, f is the inverse sensitive function of each -i,j layer, w is the inverse weight matrix between the network layers. The numerical simulation of the

neurons and networks was doing with the LabVIEW soft, version 8.2 from National Instruments. Icons and diagram of some of the virtual proper LabVIEW instruments designed specially for these investigations are shown in figs.9-11.

Figure 9. Icon of the virtual LabVIEW instrument for the assisted theoretical research of the simple

linear neuron

Figure 10. Icon of the virtual LabVIEW instrument for the assisted theoretical research of the linear neural network

Figure 11. Part of the block diagram of the virtual LabVIEW instrument for the assisted theoretical research of the linear neural network

The simulation consisted in the simulation of the sensitive functions, some different neuron types, some simple layers and complex neural network. The assisted research was made to determine the error characteristics after each iteration and to trace the matrix target t in the same characteristics with the output a and compare them. All the virtual instruments worked on-line, to see easily what are the changes of the error or of the trace of the output, comparing with the target, when was

changed the sigmoid bipolar gain, teaching gain ν, the inputs p, the weights w, and the bias b and the number of neurons in each of the layers. Some results of the assisted research of the different neurons types, the simple neural network and the complex neural network are shown in figs.12-18.

87

No.3 / October 2010

88

No.3 / October 2010

89

No.3 / October 2010

90

No.3 / October 2010

All virtual instrumentation were used to simulate some more important neural network with the goal to establish one new form of the network with very quickly approach to the target and with minimum of the errors. After simulation of the neural network form the figs. 2-7 we can remark the followings: the time delay with the parameter d determines one general possibility to adjust the parameters, but it is necessary to respect the essential condition that d must be one odd number comparing with the next layer to assure the alternative oscillation near the target curve; in the network with many time-

2delay, the delay parameter d must be odd 1number comparing with d ; the closed loop with

time-delay applied with one weight matrix can determine the instability of the network solution. To eliminate some of the deficiencies of the researched neural network, we were proposed one new structure of the neural network what will be analyzed in the paper. The proposed neural network was Bipolar Sigmoid Hyperbolic Tangent Neural Network with Time Delay and Recurrent Links (BSHTNN(TDRL)) the network what accept the teaching proposed low, by applied the inverse sensitive function.

V. ASSISTED RESEARCH OF THE P R O P R E N E U R A L N E T W O R K (BSHTNN(TDRL))

Assisted research of new neural network contents the simulation of the proposal structure with the same input, output, target, number of the neurons in each layers and teaching gain data, but in different cases of the structure of the network. To compare in the same conditions we used the simulation in different cases for the same number of iteration and for the same input data, with the matrix for weights and biases initialized at first values to zero. The icon of the LabVIEW VI is shown in fig.20.

The researched cases of the neural network was: without time-delay; with the time- delay

1after output a (t); with the time- delay after 1 2output a (t) and a (t); with the time-delay after

1a (t) and one recurrent link between the output and the input vector. For the simulation was used one proper virtual LabVIEW instrument designed by use the neural network type BSHTNN(TDRL) fig.19.

91

No.3 / October 2010

Figure 19. The block schema of the proposed new neural network type BSHTNN(TDRL)

Figure 20. The icon and part of block schema of the propre LabVIEW virtual instrument for Bipolar Sigmoid Hiperbolic Tangent Neural Network with Time Delay and Recurrent Links (BSHTNN(TDRL))

The part of the complex virtual program of the proposed neural network is shown in figure 20.

Mathematical model of the proposed neural network have the following form:

(12)

iwhere: n is the input in each senzitive functions; i,j iw - weights matrices; p- input vector; a- output

from each layer of the network; a- sigmoid bipolar hiperbolic tangent gain.

With this mathematical mmodel was designed one new proper virtual LabVIEW instrument for the assisted research of the neural network. Some results of the nnumerical simulation, byu changing some value or numeber of data from the network are presented in figs.21- 34.

92

No.3 / October 2010

93

No.3 / October 2010

94

No.3 / October 2010

95

No.3 / October 2010

96

No.3 / October 2010

97

No.3 / October 2010

98

No.3 / October 2010

99

No.3 / October 2010

VI. DISCUTION AND FUTURE WORKThe results of the weight matrix after obtain

the minimum of the error function are shown in figs.21-34, after application one double sigmoid hyperbolic tangent bipolar neural network. We can see that after 113 number of iterations process was obtained the minimum output error, under the 0.002, for each point of the curve.

The numerical simulation shown that one of the most important influence in the optimization of the output way, to approach to the target is the teaching algorithm, gain, number of neurons in each layer, dependences between the number of the neurons, time delay and where will be applied, dependences between the time delay form each layers, recurrent links, sensitive function and the number of iterations. We observe that the small teaching gain, 0.1, determine one sensitive and stable approach to the target and one big teaching gain, for example 0.2 or 0.3, determine one bigger oscillation with different magnitude of the output, balanced near the target way. After the simulation of the double bipolar sigmoid hyperbolic tangent neural network we could remark the followings: the increase of the sigmoid bipolar gain determines minimization of the errors in the end of curve and increase errors in the middle of curve; one big difference between input and target data determines divergence (-9, or -10 with the target -0.4); increasing the teaching gain over than one limit determines instability (0.6 compare with 0.1). The time delay applied in each layers must alternate, if in one layer is applied one step of time delay, in the second must be applied two time delay steps. The number of neurons of the output layer must be double from the precedent.

By using the on-line work of the virtual LabVIEW instrumentation was possible to choose the optimal values of the weight and biases matrix to obtain one smaller errors and one fast approach after one small number of iterations.

The paper shown some of the more important neurons and neuron network types, proper mathematical models for them, how can teaching these networks and what are the results after numerical simulation with proper virtual LabVIEW instrumentation. All created virtual instruments work on-line and it is possible to see the influences of the input elements, weights, biases or of the number of the neurons in hidden layer or in the input data layer. It is possible to see on-line what is happened when was changed the target form of the curve, the components of some layers, the sensitive functions or the teaching gain.

With this instrumentation we can choose the optimal form of the neural network concerning the type of the neurons in each layer, the neuron number and the biases, weights, input matrix and the teaching gain. The results and the created virtual LabVIEW instrumentation can be used in many other mechatronic guided applications, to perform the error between the target and the output and to obtain the short time of convergence.

The virtual proper LabVIEW instrumentation designed for these research activities open the way to the on-line optimization of the many other application what use the complex neural network.

Front panel of the virtual instrumentation work friendly, we can create easily all complex neural network for different application and we can choose on-line all network's parameters, like a biases and weights matrices, sensitive functions and number of neurons in each layer, teaching and sigmoid bipolar gains with the finally goal to obtain the minimum of the gradient error, with minimum number of iterations.

Showed algorithm, virtual instrumentation, proper mathematical models and the results, open the way to the optimal design of the complex neural network. In the future work will be analyzed other sensitive functions and the neural network by combined different types of these functions. The future work will be the application of the neural network to the optimal answer of the dynamic behavior with intelligent damper and proper intelligent vibration automation schema.

VII. CONCLUSIONThe paper was shown one assisted research of the more common neural networks and proposed one new neural network what introduce more rapidly convergence to the imposed target. With the proper mathematical model was possible to obtain one convergence without imposed input data, with small number of iterations and without teaching law based by teaching network with the input- target data pairs. The proposed mathematical model and the virtual proper LabVIEW instrumentation open the way to develop new generation of the intelligent systems and applied them in mechanical and aeronautical applications.

REFERENCES[1] Blelloch, G., & Rosenberg, C.R. “Network

learning on the Connection Machine” Proc. of the Tenth International Joint Conference on Artificial Intelligence. Dunno, pp. 323-326, 1987.

[2] C y b e n k o , G . A p p r o x i m a t i o n b y superpositions of sigmoid function, Mathematics of Control, Signals, and Systems, vol. 2., pp.303–314, 1989

100

No.3 / October 2010

[3] Elman, J.L.Finding structure in time, Cognitive Science, 14, pp.179-211, 1990.

[4] Fukushima, K. Cognitron: A self- organizing multilayered neural network, Biological Cybernetics, 20, pp.121-136,1975.

[5] Hartman, E.J., Keeler, J.D.,&Kowalski, J.M. Layered neural network with Gaussian hidden units as universal approximations, Neural Computation, 2(2), pp.210-215, 1990.

[6] Hopfield, J.J. Neural networks and physical systems with emergent col lect ive computational abilities, Proc.of the National Academy of Sciences, 81, pp.3088-3092, 1984.

[7] Lippmann, R.P. An introduction to computing with neural nets, IEEE Transactions on Acoustic, Speech, and Signal Processing, 2(4), pp.4-22, 1987.

[8] Minsky, M., & Papert, S. Perceptron: An Introduction to Computational Geometry, The MIT Press, 1969.

[9] Rosenblatt, F. Principle of Neurodynamics, New-York: Spartan Book.

[10] Dimith, H., Beale M.& Hagan M.: TMNeural Network Toolbox 6- User Guide, The MathWorks, Inc. 3 Apple Hill Drive Natick, MA 01760-2098, USA.

[11] Olaru, A., Olaru S., Ciupitu, L. Assisted research of the neural network by bach propagation algorithm, OPTIROB 2010 International Conference, Calimanesti, Romania, The RPS Singapore Book, pp.194-200 , 2010.

[12] Olaru, A., Olaru, S., Paune D., Ghionea A. Assisted research of the neural network, OPTIROB 2010 International Conference, Calimanesti, Romania, The RPS Singapore Book, pp.189-194 , 2010.

[13] Olaru, A., Olaru, S., Paune, D. Optimisation of the Neural Network by using the LabVIEW Instrumentation, IEEE ICMERA 2010 International Conference, Bucharest, Romania

101

NATIONAL PROFESSIONAL ASSOCIATION OF HYDRAULICS AND PNEUMATICS IN ROMANIA