ELEMENTS OF MECHANICAL ENGINEERING · (RBT: L1, L2 and L3) MODULE-5 Lathe: Principle Of Working of...

ELEMENTS OF MECHANICAL

ENGINEERING

18EME15 /18EME25

ATME COLLEGE OF ENGINEERING

VISION

Development of academically excellent, culturally vibrant, socially responsible and globally competent human resources.

MISSION

To keep pace with advancements in knowledge and make the students competitive and

capable at the global level.

To create an environment for the students to acquire the right physical, intellectual,

emotional and moral foundations and shine as torch bearers of tomorrow's society.

To strive to attain ever-higher benchmarks of educational excellence.

DEPARTMENT OFMECHANICAL ENGINEERING

VISION

To impart excellent technical education in mechanical engineering to develop technically competent, morally upright and socially responsible mechanical engineering professionals.

MISSION:

To provide an ambience to impart excellent technical education in mechanical engineering.

To ensure state of-the- art facility for learning, skill development and research in mechanical engineering.

To engage students in co-curricular and extra-curricular activities to impart social & ethical values and imbibe leadership quality.

PROGRAM EDUCATIONAL OBJECTIVES (PEO’S)

After successful completion of program, the graduates will be

PEO 1: Graduates will be able to have successful professional career in the allied areas and be proficient to perceive higher education.

PEO 2: Graduates will attain the technical ability to understand the need analysis, design, manufacturing, quality changing and analysis of the product.

PEO 3: Work effectively, ethically and socially responsible in allied fields of mechanical engineering.

PEO 4: Work in a team to meet personal and organizational objectives and to contribute to the development of the society in large.

PROGRAM OUTCOMES (PO’S)

The Mechanical engineering program students will attain:

PO1. Engineering knowledge: Apply the knowledge of mathematics, science, engineering

fundamentals, and an engineering specialization to the solution of complex engineering problems

PO2. Problem analysis: Identify, formulate, research literature, and analyze complex engineering problems reaching substantiated conclusions using first principles of mathematics, natural sciences, and engineering sciences

PO3. Design/development of solutions: Design solutions for complex engineering problems and design system components or processes that meet the specified needs with appropriate

consideration for the public health and safety, and the cultural, societal, and

environmental considerations

PO4. Conduct investigations of complex problems: Use research-based knowledge and research methods including design of experiments, analysis and interpretation of data, and synthesis of the information to provide valid conclusions

PO5. Modern tool usage: Create, select, and apply appropriate techniques, resources, and modern engineering and IT tools including prediction and modeling to complex engineering activities with an understanding of the limitations

PO6. The engineer and society: Apply reasoning informed by the contextual knowledge to assess societal, health, safety, legal and cultural issues and the consequent responsibilities relevant to the professional engineering practice

PO7. Environment and sustainability: Understand the impact of the professional engineering solutions in societal and environmental contexts, and demonstrate the knowledge of, and need for sustainable development

PO8. Ethics: Apply ethical principles and commit to professional ethics and responsibilities and norms of the engineering practice

PO9. Individual and team work: Function effectively as an individual, and as a member or leader in diverse teams, and in multidisciplinary settings

PO10. Communication: Communicate effectively on complex engineering activities with the engineering community and with society at large, such as, being able to comprehend and

write effective reports and design documentation, make effective presentations, and give and receive clear instructions

PO11. Project management and finance: Demonstrate knowledge and understanding of the engineering and management principles and apply these to one’s own work, as a member and leader in a team, to manage projects and in multidisciplinary environments

PO12. Life-long learning: Recognize the need for, and have the preparation and ability to engage in independent and life-long learning in the broadest context of technological change

PROGRAM SPECIFIC OUTCOMES (PSO’S)

After successful completion of program, the graduates will be

PSO 1: To comprehend the knowledge of mechanical engineering and apply them to identify, formulate and address the mechanical engineering problems using latest technology in a effective manner.

PSO 2: To work successfully as a mechanical engineer in team, exhibit leadership quality and provide viable solution to industrial and societal problems.

PSO 3: To apply modern management techniques and manufacturing techniques to produce products of high quality at optimal cost.

PSO 4: To exhibit honesty, integrity, and conduct oneself responsibly, ethically and legally, holding the safety and welfare of the society paramount.

Course Code Course Title Core/Elective Prerequisite Contact Hours Total Hrs/

Sessions L T P

18ME15/25

Elements of

Mechanical

Engineering

Core

BASIC SCIENCE 4 - - 50

Course

Objectives

Course objectives: This course (18ME15/25) will enable students to:

CLO1: Learn the fundamental concepts of energy, its sources and conversion.

CLO2: Comprehend the basic concepts of thermodynamics.

CLO3: Understand the concepts of boilers, turbines, pumps, internal combustion engines and

refrigeration.

CLO4: Distinguish different metal joining techniques.

CLO5: Enumerate the knowledge of working with conventional machine tools, their specifications

Topics Covered as per Syllabus

MODULE-I

Sources of Energy: Introduction and application of energy sources like fossil fuels, Hydel, Solar, Wind, Nuclear fuels

and Bio-fuels. Environmental issues like Global Warming and Ozone Depletion

Basic Concepts of Thermodynamics: Introduction, States, Concepts of work, Heat, Temperature, Zeroth law, 1st

Law, 2nd Law and 3rd Laws of thermodynamics. Concept of Internal energy, Enthalpy and entropy (Simple

Numericals)

Steam: Formation of Steam and Thermodynamic properties of steam (Simple Numericals)

(RBT: L1, L2 and L3)

MODULE-2

Boilers: Introduction to Boilers, Classification, Lancashire boiler, Babcock and Wilcox Boiler, Introduction to Boiler

mounting and accessories (No sketches).

Turbines: Hydraulic Turbines- Classification and specification, Principles and operation of Pelton Wheel Turbine,

Francis Turbine and Kaplan Turbine (Elementary Treatment only)

Hydraulic Pumps: Pumps, Introduction, Classification and specification of Pumps, Reciprocating pump and

Centrifugal Pump, Concept of Cavitation and Priming.


MODULE - 3

Internal Combustion Engines

Classification, IC engines parts, 2 and 4 stroke petrol and 4 stroke diesel engines. P-V diagrams of Otto and Diesel

cycles. Simple problems on indicated power, brake power, indicated thermal efficiency, brake thermal efficiency,

mechanical efficiency and specific fuel consumption.

Refrigeration and Air conditioning

Refrigeration – Definitions – Refrigerating effect, Ton of Refrigeration, Ice making capacity, COP, relative COP and Unit of refrigeration. Refrigerants, Properties of refrigerants, List of commonly used refrigerants, Principle and

working of vapor compression refrigeration and vapor absorption refrigeration. Domestic refrigerator, Principles and

applications of air conditioners, window and split air conditioners.


MODULE-4

PROPERTIES, COMPOSITION AND INDUSTRAIL APPLICATIONS OF ENGINEERING MATERIALS:

Metals- Ferrous: Cast Iron, Tool steels and stainless steels.

Non-Ferrous: Aluminum, brass, bronze

Polymers: Thermoplastics and thermo setting polymers.

Ceramics: Glass, optical fiber glass, cements

Composites- Fiber reinforced composites, Metal Matrix composites.

Smart Materials: Piezoelectric materials, Shape memory alloys, Semiconductors and insulators.

JOINING PROCESSES: SOLDERING, BRAZING AND WELDING

Definitions, Classification and Methods of soldering, Brazing and welding

Brief description of arc welding, Oxy-acetylene welding, TIG welding and MIG welding

BELT DRIVES

Open & crossed belt drives, Definitions- slip, creep, velocity ratio, derivations for length of belt in open and crossed

belt drive, ratio of tension in flat belt drives, advantages and disadvantages of V belts and timing belts, simple

numerical problems.

GEAR DRIVES: Types- Spur, helical, bevel, worm and rack and pinion, Velocity ratio, advantages and disadvantages over belt drives,

simple numerical problems on velocity ratio


MODULE-5

Lathe: Principle Of Working of a Center Lathe, Parts of a Lathe. Operations on Lathe- Turning, Facing, Knurling, Thread

Cutting, Drilling, Taper Turning by Tailstock Offset Method and Compound Slide Swiveling Method. Specification of Lathe

Milling Machine: Principle of Milling, Types of Milling Machines, Working Of Horizontal and Vertical Milling Machines.

Milling Processes -P lane Milling, End Milling, Slot Milling, Angular Milling, Form Milling, Straddle Milling, and Gang

Milling

(Layout of sketches of the above machines needs to be dealt. Sketches need to be used only for explaining the operations

performed on the machines)

Introduction to Advanced Manufacturing Systems

Computer Numerical Control (CNC): Introduction, Components of CNC, Open Loop and Closed Loop Systems,

advantages of CNC, CNC Machining centers and Turning Centers.

Robots: Robot Anatomy, Joints and Links, Common Robot Configurations, Applications of Robots in material handling,

Processing and assembly and inspection.


List of Text Books

1. V.K.Manglik, “Elements of Mechanical Engineering”, PHI Publications, 2013. (Module-1,2,4,5) 2. MikellP.Groover, “Automation, Production Systems & CIM”, 3rd Edition, PHI (Module 3. K.R.Gopalkrishna, “A text Book of Elements of Mechanical Engineering”- Subhash Publishers, Bangalore.

(Module -1,2,3,4,5)

List of Reference Books

1. S.TrymbakaMurthy, “A Text Book of Elements of Mechanical Engineering”, 4th Edition 2006, Universities Press (India) Pvt Ltd, Hyderabad.

2. K.P.Roy, S.K.HajraChoudhury, Nirjhar Roy, “Elements of Mechanical Engineering”, Media Promoters & Publishers Pvt Ltd,Mumbai,7th Edition,2012 3. Pravin Kumar, “Basic Mechanical Engineering”, 2013 Edition, Pearson.

Energy Resources and Steam

MODULE-1 ENERGY AND STEAM

Objective:

• To understand importance of energy for country economical growth. • To study the different energy resources like fuels, solar, hydro, wind energy etc.

To understand the difference between Renewable sources of energy & Non-renewable energy sources

Contents

1.1 Energy Sources: 1.2 Renewable sources of energy

1.3 Non-renewable energy sources

1.4 Fuels

1.5 Solar Enegy

1.6 Hydroelectric power plant

1.7 Wind Energy

1.8 Nuclear Energy.

1.9 Steam

1.10 Boilers

ENERGY Energy is an fundamental concept in physics, with applications throughout the

natural sciences.Can you imagine life without lights, fans, cars, computers and television

or, of fetching water from the well and river? This is what life would have been like had man not discovered the uses of energy – both renewable and nonrenewable sources.

Energy is the driving force for humans and machines, without energy the whole world will comes to stand still (halt).

The total energy of a system can be subdivided and classified in various ways. For example, it is sometimes convenient to distinguish kinetic energy from potential

energy. It may also be convenient to distinguish gravitational energy, electrical energy, thermal energy, and other forms. These classifications overlap; for instance thermal

energy usually consists partly of kinetic and partly of potential energy Energy is the primary and most universal measure of all kinds of work by human

beings and nature. Most people use the word energy for input to their bodies or to the machines. 1.1 ENERGY SOURCES

The energy resources available can be divided in to Primary energy resources: These can be defined as sources, which provide a

net supply of energy. Coal, oil, uranium etc. are examples of this type. The primary fuels

only can accelerate growth but their supply is limited. It becomes very essential to use these fuels sparingly. Primary fuels contribute considerably to the energy supply.

http://en.wikipedia.org/wiki/Concepthttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Systemhttp://en.wikipedia.org/wiki/Kinetic_energyhttp://en.wikipedia.org/wiki/Potential_energyhttp://en.wikipedia.org/wiki/Potential_energy


Secondary energy resources: Secondary fuels produce no net energy. Though it may be necessary for the economy, these may not yield net energy. Secondary sources are like solar, wind & water energy.

1.1.1 Renewable sources of energy

Energy sources which are continuously produced in nature and are essentially inexhaustible are called renewable energy sources.

4. Direct solar energy

5. Wind energy

6. Tidal energy

7. Hydel energy

8. Ocean thermal energy

9. Bio energy

10. Geo thermal energy

1.1.2 Non-renewable energy sources

Energy sources which have been accumulated over the ages and not quickly replenishable when they are exhausted

1. Fossil fuels. 2. Nuclear fuels 3. Heat traps

1.1.3 Advantages of renewable energy sources 1. Non exhaustible.

2. Can be matched in scale to the need and can deliver quality energy.

3. Can be built near the load point.

4. Flexibility in the design of conversion systems.

5. Local self sufficiency by harnessing locally available renewable energy.

6. Except biomass, all other sources are pollution free.

1.1.4 Disadvantages

1. Intermittent nature of availability of energy such as solar, wind, tidal etc. is a major

setback in the continuous supply of energy.

2. Solar energy received at the earth is dependent on local atmosphere conditions, time of

the day, part of the year etc.

3. Sources such as wind, tidal etc. are concentrated only in certain regions.


1.2 Calorific Value of Fuels The efficiency of fuel is expressed in terms of calorific value.

Calorific value of a fuel is defined as the total quantity of heat liberated by

burning a unit mass or volume of fuel completely.

Higher Calorific Value (H.C.V.): The Higher Calorific Value of a fuel is defined as the total heat

liberated by complete combustion of one kg /litre /m3 of fuel, including the

heat recovered from condensed water vapour.

Lower Calorific Value (L.C.V.):

The Lower Calorific Value of a fuel is defined as the heat liberated by complete

combustion of one kg /litre /m3 of fuel, excluding the heat recovered from

condensed water vapour.

L.C.V. = H.C.V. - (mass of H2O x Latent Heat)

1.3 Combustion

Principle of Combustion

Combustion refers to the rapid oxidation of fuel accompanied by the

production of heat, or heat and light. Complete combustion of a fuel is

possible only in the presence of an adequate supply of oxygen.

Oxygen (O2) is one of the most common elements on earth making

up 20.9% of our air. Rapid fuel oxidation results in large amounts of

heat. Solid or liquid fuels must be changed to a gas before they will

burn. Usually heat is required to change liquids or solids into gases.

Fuel gases will burn in their normal state if enough air is present.

Most of the 79% of air (that is not oxygen) is nitrogen, with traces

of other elements. Nitrogen is considered to be a temperature

reducing dilutant that must be present to obtain the oxygen required

for combustion.

Nitrogen reduces combustion efficiency by absorbing heat from the

combustion of fuels and diluting the flue gases. This reduces the


heat available for transfer through the heat exchange surfaces. It also increases the volume of combustion by-products, which then have to travel through the heat exchanger and up the stack faster to allow the introduction of additional fuel air mixture.

This nitrogen also can combine with oxygen (particularly at high

flame temperatures) to produce oxides of nitrogen (NOx), which are toxic pollutants.

Carbon, hydrogen and sulphur in the fuel combine with oxygen in the air to form carbon dioxide, water vapour and sulphur dioxide, releasing 8084 kcals, 28922 kcals & 2224 kcals of heat respectively. Under certain conditions, Carbon may also combine with Oxygen to form Carbon Monoxide, which results in the release of a smaller

quantity of heat (2430 kcals/kg of carbon) Carbon burned to CO2

will produce more heat per pound of fuel than when CO or smoke are produced.

C + O2 → CO 2 + 8084 kCals/kg of Carbon 2C + O2 → 2 CO + 2430 kCals/kg of Carbon 2H 2 + O2 → 2H2O + 28,922 kCals/kg of Hydrogen S + O2 → SO2 + 2,224 kCals/kg of Sulphur

Each kilogram of CO formed means a loss of 5654 kCal of heat. (8084-2430).

1.4 CLASSIFICATION OF FUELS: The fossil fuels have been classified according to their: 1. State of occurrence 2. State of aggregation. According to the state of occurrence, we have: (a) Natural or primary fuels, which are found in nature. E.g. wood, peat, coal, petroleum, natural gas etc.

(b) Artificial (or) secondary fuels are those which are prepared from the primary fuels.

E.g., charcoal, coke, kerosene oil, petrol, coal gas, oil gas, producer gas, blast furnace gas etc.


The second classification is based upon their state of aggregation like: (a) solid fuels; (b) liquid fuels; (c) gaseous fuels.

Fig .1 Classification of fuels

1.4.1 SOLID FUELS

Solid fuels are of two types (1) Natural Solid fuels

(2) Artificial Solid fuels

(1) Natural Solid Fuels: Natural solid fuels are of following types;

(a) Wood

(b) Peat

(c) Lignite or Brown Coal

(d) Bituminous Coal

(e) Anthracite


(a) Wood:

Mainly consists of Carbon, Hydrogen and water.

Its Calorific Value varies according to the kind of wood & water content in it.

It is not used as commercial fuel.

It is raw material for other solid fuels.

(b) Peat:

It is first stage which is derived from wood & vegetable matters & is derived from earth.

It contains 20% to 30% of water.

It burns without smoke or soot formation.

Its calorific value is approx. 14,500 KJ/kg.

(c) Lignite or Brown Coal:

It is very soft, inferior quality coal.

It contains 60% or more Carbon.

It also contains 15% to 20% moisture.

It is used as low grade fuel.

It is non - caking type of coal.

It burns with large smoky flame having C.V. equal to 21,000 kJ/kg.

(d) Bituminous Coal:

It is soft & shiny black in appearance.

It contains about 70% Carbon & 20% - 30% Volatile matter.

It burns with long yellow and smoky flame.

It may be caking or non - caking type.

Its calorific value is approx. 31,500 KJ/kg.

(e) Anthracite Coal

It is very hard & brittle.

It contains 90% or more Carbon.

It also contains 8% to 10% volatile matter.

It is used as High grade fuel.

It is non - caking type of coal.

It does not give smell when burning.


It’s Calorific. Value is approx. 36,000 kJ/kg.

(2) Artificial Solid Fuels: Artificial Solid Fuels are of following types;

(a) Wood Charcoal

(b) Coke

(c) Briquetted Coal

(d) Pulverised Coal

(a) Wood Charcoal

It is obtained by burning wood in retorts with insufficient air to a temp. of 310ºC.

It contains 80% to 90% Carbon.

It can burn easily without smoke.

Its Calorific Value is approx. 28,000 kJ/kg.

(b) Coke:

It is made by burning Bituminous coal by driving out its volatile elements in absence of air.

It is hard, brittle & porous.

The coke formation process is called

Carbonization.

It contains 85% to 95% Carbon.

Its Calorific Value is approx. 32,500 kJ/kg.

(c) Briquetted Coal:

It consists of finely ground coal mixed with proper binder and pressed

together into Briquettes(Blocks).

This increases heating value of coal & decreases the losses.

(d) Pulverised Coal:

It is powder form of coal.

It is formed by crushing the coal.

This fine particle atomised coal is burnt by supplying the air to it.

Low grade fuel is efficiently burnt by pulverising it.

It gives better control, complete combustion with less excess air, higher flame temp. etc.


QUID FUELS:

1.4.2 LIQUID FUELS:

Liquid fuels are of two types;

(1) Natural Liquid fuels

(2) Artificial Liquid fuels

(1) Natural Liquid Fuels: Natural Liquid fuels are of following types;

(a) Crude petroleum

(b) Fossile fuels.

(a) Crude Petroleum:

It is obtained from natural reservoirs in the earth’s crust through wells.

Distillation is the process of heating the

crude petroleum and condensing the vapour thus formed at various temp. and pressures.

By Distillation of crude oil, petrol, kerosene, diesel, fuel oils, tar etc… are obtained.

(b) Fossile Fuels:

Due to reactions of Vegetable matters & animals embodied with earth, after very

long period at high pressure and temperature fossil fuels are formed.

(2) Artificial Liquid Fuels: Artificial Liquid fuels are of following types;

(a) Hydrocarbons

(b) Vegetable matter (Alcohol)

(a) Hydrocarbons:

Hydrocarbon is a substance having Carbon & Hydrogen as basic constituents.

Most of artificial liquid fuels are obtained from mixture of different Hydrocarbons.

The main Hydrocarbons are;


(1) Paraffins (CnH2n+2)

(2) Olefines (CnH2n) /Ring compound

(3) Naphthenes (CnH2n) /Chain compound

(4) Aeromatics or Benzenes (CnH2n - 6)

(b) Vegetable matter (Alcohol)

(a) Petrol:

Petrol or Gasoline is obtained by distillation of crude oil from 65º to 220ºC.

Its Calorific value is 44,250 kJ/kg.

It is used for light petrol engines, aviation and small industrial installation.

(b) Kerosene/Paraffin oil:

Kerosene or Peraffin oil is obtained by distillation of crude oil from 220º

to 345ºC.

It is heavier and less volatile than petrol.


It is used for heavy road traction, tractors and internal combustion engines.

(c) Fuel oil:

Fuel oil is obtained by distillation of crude oil from 345º to 470ºC.


It is heavy and non - volatile.

(d) Alcohol:

It is formed by fermentation of vegetable matter.

Widely used as commercial fuel.

Its calorific value is 26,800 kJ/kg.

1.4.3 GASEOUS FUELS:

Gaseous fuels are of two types;

(1) Natural Gaseous fuels

(2) Artificial Gaseous fuels


(1) Natural Gas:

Natural gas consists of mainly methane & ethane, propane and also oxygen, Carbon monoxide, Nitrogen, and Carbon dioxide etc.

Its calorific value varies from 35,500 kJ/m3 to 46,000 kJ/m3.

(2) Artificial Gaseous Fuel:

Artificial gaseous fuels are prepared gases of fixed composition like

acetylene(C2H2), methane(CH4), ethylene(C2H4) etc… The artificial industrial gases are Coal gas, Producer gas, Water gas, Mond gas, Blast

furnace gas, Cock - oven gas, Marsh gas etc…

(i)Coal Gas/Illuminating Gas:

It is obtained by distilling coal in retorts. It mainly consists of Hydrogen, CO, CO2, CH4, Nitrogen etc…

Its calorific value varies from 21,000 kJ/m3 to 25,000 kJ/m

3.

(ii) Producer Gas:

It is obtained by passing insufficient air through a bed of incandescent coke or

charcoal in gas producer.

It consists of CO, CO2,H2, N2

It is cheaply available.


(iii)Water Gas/Blue Gas:

It is obtained by passing steam through

Incandescent bed of cock or coal containing carbon.

It burns with blue flame and hence also called blue gas.


(iv) Mond gas:

It is obtained by injecting large quantity of steam in producer.

It is used in gas engines.

Its calorific value is 5,800 kJ/m3.

(v) Blast - furnace Gas:


It is obtained as by-product in the production of Pig iron.

It is mixture of H2, CO, CO2, N2 and CH4.

It contains considerable amount of dust in it.


(vi) Coke - Oven Gas:

It is produced by high temp. carbonization of bituminous coal.

It is by - product from coke oven.

It is mixture of methane & hydrogen.


(vii) Marsh Gas:

It is a simple Hydrocarbon (Methane)

produced in nature by the decay of vegetable matters under water.


(viii) Oil Gas:

Produced by vaporisation and thermal cracking of oils and steam.

Its calorific value is 17,000 to 25,000 kJ/m3.

1.4.4 Requirements of a Good Fuel

It should have low ignition temperature.

It should have high calorific value.

It should freely burn with high combustion efficiency.

It should not produce harmful gases or smoke.

It must produce less ash.

It must be cheaper and should be easily available.

Its storage must be easy.

Its transportation & handling should be easy. It should not react with material of furnace.

1.5 Solar energy Solar energy is the most readily available source of energy. It does not belong to

anybody and is, therefore, free. It is also the most important of the non-conventional sources of energy because it is non-polluting and, therefore, helps in lessening the

greenhouse effect. The sun constantly delivers 1.36 kW of energy per square meter to the earth. The energy which reaches the earth surface contains both beam radiation and


diffused radiation. The radiation reaches the ground directly from the sun is called beam radiation. Diffuse radiation is that solar radiation received from the sun after its direction has been changed by reflection and scattering by the atmosphere.

The problem with solar radiation is estimation of diffused radiation & beam

radiation, both radiations are not constant. It keeps on changes every minute,hour,day

month and year. Therefore it is difficult to design a solar device which will suit to our

requirements. To harvest solar energy we need solar collectors, these collectors are

designed to absorb and store the solar energy, these devices should work more

effectively in varying temperature conditions.

1.5.1 Solar radiation

The distribution of solar radiation as a function of the wavelength is called the

solar spectrum, which consists of a continuous emission with some superimposed line

structures. The Sun’s total radiation output is approximately equivalent to that of a blackbody at 5776 K. The solar radiation in the visible and infrared spectrum fits closely

with the blackbody emission at this temperature. However, the ultraviolet (UV) region

(o0.4 mm)of solar radiation deviates greatly from the visible and infrared regions in

terms of the equivalent blackbody temperature of the Sun. In the interval 0.1-0.4 mm,

the equivalent blackbody temperature of the sun is generally less than 5776 K with a

minimum of about 4500 K at about 0.16 mm. The deviations seen in the solar spectrum

are a result of emission from the no isothermal solar atmosphere.

1.5.2

Solar

const

ant The

solar


constant is the amount of solar radiation received outside the Earth’s atmosphere on a surface normal to the incident radiation per unit time and per unit area at the Earth’s

mean distance from the Sun. The solar constant is an important value for the studies of

global energy balance and climate. Reliable measurements of solar constant can be made

only from space and a more than 20-year record has been obtained based on overlapping

satellite observations.

Solar energy harvesting

1.5.3 Liquid Flat plate collectors The flat plate collector is a device used to absorb and store solar energy. The

stored energy is used for domestic, agriculture or industrial applications. The construction of flat plate collector is very simple.

The flat plate collector consists of a metal sheet (absorber surface) exposed to the

solar radiation. This sheet absorbs both beam and diffused solar radiation. The sheet is

coated with black paint. Fluid carrying pipes are connected to back side of the metal

sheet. The liquid most commonly used is water. The lower side of metal sheet is covered

with insulating material. The transparent cover (glass) is fixed above the metal sheet,

which reduces the heat loss due to convection & radiation. The flat plate collector

efficiency is good at medium and maximum temperatures, but at low temperature the

efficiency is very low. The flat plate collectors are designed for output temperatures

ranging from 60º C to 100º C.

Fig. 2 Liquid Flat plate collectors

1.5.4 Solar pond


A solar pond is a body of water that collects and stores solar energy. Solar energy will

warm a body of water (that is exposed to the sun), but the water loses its heat unless

some method is used to trap it. Water warmed by the sun expands and rises as it

becomes less dense. Once it reaches the surface, the water loses its heat to the airthrough

convection, or evaporates, taking heat with it. The colder water, which is heavier, moves

down to replace the warm water, creating a natural convective circulation that mixes the

water and dissipates the heat. The design of solar ponds reduces either convection or

evaporation in order to store the heat collected by the pond. They can operate in almost

any climate.

A solar pond can store solar heat much more efficiently than a body of water of the same

size because the salinity gradient prevents convection currents. Solar radiation entering

the pond penetrates through to the lower layer, which contains concentrated salt solution.

The temperature in this layer rises since the heat it absorbs from the sunlight is unable to

move upwards to the surface by convection. Solar heat is thus stored in the lower layer

of the pond .

Working Principle

The solar pond works on a very simple principle. It is well-known that water or air is heated they become lighter and rise upward. Similarly, in an ordinary pond, the sun’s rays heat the water and the heated water from within the pond rises and reaches the top but loses the heat into the atmosphere. The net result is that the pond water remains at the atmospheric temperature. The solar pond restricts this tendency by dissolving salt in the bottom layer of the pond making it too heavy to rise . You can see a shematic view of a solar pond in Figure 3.


3 Schematic View of a Solar Pond

The solar pond possesses a thermal storage capacity spanning the seasons. The surface

area of the pond affects the amount of solar energy it can collect. The bottom of the pond

is generally lined with a durable plastic liner made from material such as black

polythene and hypalon reinforced with nylon mesh. This dark surface at the bottom of

the pond increases the absorption of solar radiation. Salts like magnesium chloride,

sodium chloride or sodium nitrate are dissolved in the water, the concentration being

densest at the bottom (20% to 30%) and gradually decreasing to almost zero at the top.

Typically, a salt gradient solar pond consists of three zones .

An upper convective zone of clear fresh water that acts as solar collector/receiver and

which is relatively the most shallow in depth and is generally close to ambient

temperature, gradient which serves as the non-convective zone which is much thicker

and occupies more than half the depth of the pond. Salt concentration and temperature

increase with depth, A lower convective zone with the densest salt concentration,

serving as the heat storage zone. Almost as thick as the middle non-convective zone, salt

concentration and temperatures are nearly constant in this zone .

When solar radiation strikes the pond, most of it is absorbed by the surface at the bottom

of the pond. The temperature of the dense salt layer therefore increases. If the pond

contained no salt, the bottom layer would be less dense than the top layer as the heated

water expands. The less dense layer would then rise up and the layers would mix. But

the salt density difference keeps the ‘layers’ of the solar pond separate. The denser salt water at the bottom prevents the heat being transferred to the top layer of fresh water by

natural convection, due to which the temperature of the lower layer may rise to as much

as 95°C .


Fig. 5 El Paso Solar Pond

1.6 Solar photovoltaic(PV) systems

Photovoltaics (PV) is a method of generating electrical power by converting solar

radiation into direct current electricity using semiconductors that exhibit the photovoltaic

effect. Photovoltaic power generation employs solar panels composed of a number of

solar cells containing a photovoltaic material. Solar photovoltaics power generation has

long been seen as a clean sustainable energy technology which draws upon the planet’s most plentiful and widely distributed renewable energy source – the sun. The direct conversion of sunlight to electricity occurs without any moving parts or environmental

emissions during operation. It is well proven, as photovoltaic systems have now been

used for fifty years in specialized applications, and grid-connected systems have been in

use for over twenty years . In 2013, its fast-growing capacity increased by 38 percent to a running total of 139 GW, worldwide. This is sufficient to generate at least 160 terawatt hours (TWh) or about 0.85

percent of the electricity demand on the planet. China, followed by Japan and the United States, is now the fastest growing market, while Germany remains the world's largest

producer, contributing almost 6 percent to its national electricity demands. Solar photovoltaics is now, after hydro and wind power, the third most important

renewable energy source in terms of globally installed capacity. More than 100 countries

use solar PV. Installations may be ground-mounted (and sometimes integrated with farming and grazing) or built into the roof or walls of a building (either building-

integrated photovoltaics or simply rooftop). Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells

were manufactured, and the levelised cost of electricity (LCOE) from PV is competitive with conventional electricity sources in an expanding list of geographic regions. Net

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metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries. With current

technology, photovoltaics recoup the energy needed to manufacture them in 1.5 (in Southern Europe) to 2.5 years (in Northern Europe).

Mechanism of generation

The solar cell is composed of a P-type semiconductor and an N-type semiconductor.

Solar light hitting the cell produces two types of electrons, negatively and positively

charged electrons in the semiconductors. Negatively charged (-) electrons gather around

the N-type semiconductor while positively charged (+) electrons gather around the P-

type semiconductor. When you connect loads such as a light bulb, electric current flows

between the two electrodes.

Fig.6 Solar PV system

1.7 Wind energy Wind energy is the kinetic energy associated with the movement of atmospheric

air. It has been used for hundreds of years for sailing, grinding grain, and for irrigation. Wind energy systems convert this kinetic

http://en.wikipedia.org/wiki/Feed-in_tariff


energy to more useful forms of power. Wind energy systems for irrigation and milling

have been in use since ancient times and since the beginning of the 20th

century it is being used to generate electric power. Windmills for water pumping have been installed in many countries particularly in the rural areas. Wind can be used to do work. The kinetic energy of the wind can be changed into other forms of energy, either mechanical energy or electrical energy.

Advantages of wind energy.

Wind is free, wind farms need no fuel.

Produces no waste or greenhouse gases.

The land beneath can usually still be used for farming.

A good method of supplying energy to remote areas.

Disadvantage of wind energy

The wind energy available in dilute form, hence bigger size energy conversion machines are required.

Wind energy systems are noisy in operation.

Large space is required.

High initial cost.

High maintenance cost.

Multi blade wind mill The multi blade wind mill is the oldest one which consists of 12 to 20 blades.

These blades are made of metal sheet or cloth. The multi blade wind mill is bulky and heavy, but develops huge torque to drive pump or to generate electricity.


Fig. 7 Sail type wind mill

Sail type wind mill

The sail type wind mill has 3 to 4 wings. These wings are generally made of cloth hence the weight of these wind mills are less. Each wing have the shape of a triangle. This wind mill is used for light loads.

Propeller type wing mill In this type two rotors are connected to a rotor. The rotor is

connected to a generator through a set up gear box. The blades are made of metal. The cost of the blades are too high, hence the number of blades are restricted to two numbers

only. Rotors with more than 3 to 4 blades will develop more torque than two blades.

Darries rotor Savonius rotor is a vertical shaft wind mill, this requires less structural support.

The components like gear box and generator are located at ground level.The horizontal

axis wind mill will react to wind from any direction. This wind mill will develop high initial torque, and develops lesser power output per given rotor size.


Fig.8 Darries rotor

It has two or three thin curved (egg beater) blades with airfoil cross section. The blades of Darries rotor are made lighter than propeller type wind mill. When rotating,

these airfoil blades provide a torque about the central shaft with response to a wind stream. The advantages of darries rotor wind mill are high speed, high efficiency and

low cost.

1.8 Hydro Power When it rains in hills and mountains, the water becomes streams and rivers that

run down to the ocean. The moving or falling water can be used to do work. Energy,

you'll remember is the ability to do work. So moving water, which has kinetic energy, can be used to make electricity. Today, moving water can also be used to make

electricity. Hydroelectric power uses the kinetic energy of moving water to make electricity.

Dams can be built to stop the flow of a river. Water behind a dam often forms a reservoir

Like the picture of Shasta Dam in Northern California pictured on the right. Dams are also built across larger rivers but no reservoir is made. The river is simply sent through a

hydroelectric power plant or powerhouse.


1.8.1 Hydro power plant The water behind the dam flows through the intake and into a pipe called a

penstock. The water pushes against blades in a turbine, causing them to turn. The turbine spins a generator to produce electricity. The electricity can then

travel over long distance electric lines to your home, to your school, to factories and businesses. Hydro power today can be found in the mountainous areas of states where there are lakes and reservoirs and along rivers.

Fig.9a Hydro power plant


Fig.9b Hydro power plant

Elements of hydro power station

Reservoir: The reservoir is used to store ample of water for power generation.

The dam is a massive concrete structure which is built across the reservoir. The concrete structure will block the flow of water out of reservoir. The sluice gates are built in

concrete structure which can be opened or closed to allow the water out of reservoir.

Dam: Controls the flow of water and increases the elevation to create the head. The reservoir that is formed is, in effect, stored energy.

Generator: Connects to the turbine and rotates to produce the electrical energy.

Penstock : The water from the reservoir to the power house is carried through pipe lines is called as penstock. The penstock may be a concrete pipe or metal pile.


Draft tube: The conical shaped passageway downstream of the turbine that slows the water exiting the turbine runner and allows uniform recovery of water pressure between the runner and the tailrace .

Surge tank: hydraulic structure designed to control pressure and flow fluctuations in a penstock or tunnel. It functions as a standpipe and a quick-acting reservoir that temporarily stores or releases water to the penstock.

Tailrace: The channel which directs water flow away from the powerhouse after passing through the generating turbines.

1.9 Nuclear Energy The depletion of natural resources like crude oil, natural gas and coal, this leads

to invention of alternative source of energy for survival. Uranium is the main element required to run a nuclear reactor where energy is extracted. Nuclear fission or fusion

process produce tremendous amount of heat energy. The energy released during nuclear reaction is utilized to generate electricity.

Nuclear fission: Nuclear fission is the process, where a heavy nucleus splits into two fragments of more or less of equal mass.

Neutron + Heavy nucleus → Fission fragments + Neutrons ( 2 to 3 ) + energy

92U235

+ 0N1 → 56Ba

137 + 56Kr97 + 20N

1 + Energy (The energy released by fission of I gram of U-235 is equal to that due to

combustion of 50 million tons of coal ; it is about 8.5 x 1010

J.) In the above reaction uranium-235 is used as fuel, which is available in nature.

The other reactor fuels are uranium-233 and plutonium-239 Which are prepared artificially.

The fission reaction

releases not only energy,

but also the emissions of

neutrons. Two

or three neutrons are

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emitted on the average per nucleus undergoing fission. The emitted neutrons can cause fissions in additional nuclei, thus liberating more neutrons which can cause further fissions.

Nuclear fusion: Fusion energy is a form of nuclear energy released by the fusion (combustion) of

two light nuclei( i.e. nuclei of low mass ) to produce heavier mass.

41H1 → 2He4 + 2+1 e

0

Parts of a nuclear reactor A nuclear reactor is a device which controls the nuclear fission chain reaction to

harness nuclear energy for peaceful purposes. A nuclear reactor which is used t generate

electricity, is called a nuclear power plant. In nuclear power plant, the energy released by fission is used produce

superheated steam. This turns a turbine which in turn operates an electric generator. A nuclear power plant has the following components.

i) The fissionable material of nuclear fuel

ii) The control rods

iii) The pressure vessel

iv) Cooling system

v) Heat exchanger. In a nuclear power plant nuclear power plant nuclear fuel in the form of pellets

are enclosed in several tubular claddings of steel or aluminum. This is called fuel

assembly. Enriched U-235 or Pu-239 is the fuel material. The fast neutrons released

during fission are slowed down by a moderator, usually graphite surrounding the fuel

assembly. A coolant is circulated through the reactor to remove the heat generated.

Ordinary water is most commonly used coolant. Other coolants such as heavy water,

liquid sodium, molten salts and hydro carbon liquids are also used.

Fig.10 Nuclear power plant


Rods made of boron or cadmium which are neutron absorbers are used as control rods.

The neutrons available for fission are controlled by moving the control rods in and out of the nuclear core. The rods can be used to shut down the reactor. Functioning of the

reactor is constantly monitored with the help of suitable instruments. Heat produced during fission process is absorbed by the coolant and is used to

convert water in to steam in the heat exchanger. The steam is used to rotate the steam turbine .The steam turbine is connected to a generator which generate electricity.

The entire reactor is enclosed in a concrete building with lead sheets covered inside to prevent radioactive radiations being released in to the environment.

1.10 Bio Fuels

Introduction to bio fuels

Biofuels are fuels made from recently grown plant or animal matter. Fossil fuels were

also originally plant or animal matter, but that material has spent millions of years

underground in extreme conditions and so it has changed significantly and its energy

value was concentrated. As fossil fuel supplies diminish, renewable energy resources

that can be replenished faster than we use them must be found in order for society to

continue functioning as we are accustomed. Some folks believe that biofuels, like corn

ethanol and biodiesel, could supply this renewable supply of fuel.

There are other negative environmental impacts related to fossil fuel use, in addition to

the depletion of a limited resource. Many toxic chemicals contained in fossil fuels are

released into the atmosphere upon burning of oil and coal. Biofuels are less toxic than

fossil fuels - biodiesel is less toxic than table salt, for example. In addition, carbon

released from the sequestered underground reservoirs of fossil fuels goes into the

atmosphere as carbon dioxide. Most scientists agree that the human-caused increase in

atmospheric carbon dioxide and other greenhouse gases are at least partially

influencing global temperature. Thus, fossil fuel use influences global climate

destabilization. Biofuels are touted as a potential solution (at least partially) to the

problem of greenhouse gases from fossil fuels. The biofuels still release carbon dioxide

into the atmosphere, but since the fuel comes from recently grown plants, it was

extracted from the atmosphere through photosynthesis, and will be reused by future

crops. By limiting the amount of carbon moving from the underground to the

atmosphere, the idea is to reduce the intensity of global warming.

Ethanol and biodiesel are now commonly mixed with petroleum-based fuels for sale as

transportation fuels


1.10.1 Ethanol

Ethanol is made by the biological fermenting of sugars in the feedstock. If the feedstock

does not contain sugars initially, pretreatment steps must precede the fermentation to

transform the complex starches (corn) or cellulose into simpler sugar molecules. After

the fermentation step, distillation is required to separate the ethanol from water.

1.10.2 Biodiesel

The diesel engine was originally designed to run on peanut oil. Modern diesel engines

are designed to run on petroleum (fossil fuel) diesel, but can still run on vegetable oil if

the oil’s viscosity is low. Warming the oil is required to lower the viscosity, so some alterations must be made to the fuel supply to the engine. The main reason for the use of

petroleum diesel is its low cost and slightly higher energy value. Some people are

promoting a return to vegetable oil for reasons of renewability and low pollution. By

converting the oil to biodiesel, the energy value is increased and viscosity is lowered.

This fuel can then be mixed with petroleum diesel (up to 20% mix (B20) can be used

safely in any diesel engine) or can be used pure in many vehicles.

1.10.3 Bio Gas

Since today’s infrastructure for transport is based on liquid fuels, the introduction of

gaseous fuels into the transport sector is slow and represents a challenge for future

transport strategies. Nevertheless, vehicles which use gaseous fuels in place of liquid

fuels are already operating. Today most of them run on natural gas. Many automotive

manufacturers already offer pure or bivalent natural gas vehicles as standard models.

One of the promising future options for sustainable transport fuels is the subsidization of

natural gas by biomethane. Biomethane is the most efficient and clean burning biofuel

which is available today. It can be produced from nearly all types of biomass including

wet biomass which is not usable for most other biofuels. Another motivation for using

gaseous biofuels for transport applications is the opportunity of diversifying feedstock

sources.

1.10.4 Bio fuels used in engineering application

Bio diesel and ethanol used in Automobiles

Bio gas used to cooking purpose

Bio fuels used in rural electrification

Bio fuels used in agriculture sector

Bio fuels used in thermal applications


1.10.5 Comparison of biofuels with petroleum fuels

SL.NO Characteristics Petroleum fuels(Diesel)

Bio

fuels(Honge)

1 Calorific Value(kJ/kg) 42500 38987

2 Viscosity at 40° 2-5 4.9-5.7

3 Cetane number 45-55 40-48

4 Flash point(°C) 56 174

5 Specific gravity 0.820 0.927

6 Density (kg/m3) 820 927

1.11 Steam formation and Properties

1.11.1 Introduction:

Steam is the gaseous phase of water. It utilizes heat during the process and carries large

quantities of heat later. Hence, it could be used as a working substance for heat

engines. Steam is generated in boilers at constant pressure. Generally, steam may be

obtained starting from ice or straight away from the water by adding heat to it. Steam

exists in following states or types or conditions.

(i) Wet steam (saturated steam) (ii) Dry steam (dry saturated steam) (iii) Superheated steam (iv) Supersaturated steam water, which is one of the Pure Substance, exists in three phases:

(a) Solid phase as ice (freezing of water) (b) Liquid phase as water (melting of ice) (c) Gaseous phase as steam (vaporization of water)

Water could be used as coolant and water vapor is used as a working fluid for the operation of Steam Engines and Steam Turbines.


1.11.2 Properties of Steam

Take one kg of water at 0oC in a cylinder fitted with piston. Place a known

weight on the piston to have constant pressure acting on the piston. Insert a thermometer to monitor the temperature. Start heating the cylinder at a constant rate and note down the temperature along with the quantity of heat added. Plot the values on a graph with the quantity of heat supplied taken along x – axis and the temperature along y – axis. The nature of the graph is shown in the figure 11

Fig .11

Initially the temperature starts increasing steadily with heat addition. This

continues up to the point ‘f ‘ on the graph. At this point water is no more able to take in the heat in liquid phase. Water starts changing its phase to vapor (steam). This change in

phase from liquid to vapor is called boiling. The change of phase occurs at constant

temperature and at point ‘g ‘ the water is completely vaporized. Further heating results in steady increase in temperature of steam.

The water is said to be saturated at point ‘f’. we call the point ‘f’ saturated liquid point. Similarly, the steam is said to be saturated at point ‘g’, and we call the point ‘g’ the saturated vapor point. The constant temperature at which boiling takes place is called

the saturated temperature (Tsat)

By definition heat added at constant pressure is given the name enthalpy denoted by ‘h’. The variable along x – axis now becomes enthalpy. We can define enthalpy at salient points on the graph as follows


Fig.12

hf = Enthalpy of saturated liquid

(heat added from 00 C till the point ‘f’)

hfg = Enthalpy of evaporation

(amount of heat added to convert saturated liquid to saturated vapour)

hg = Enthalpy of saturated steam

(amount of heat added from 00 C till the point ‘g’)

The quantity hf is also called the sensible heat because we can sense the change

in temperature from 0 to f. The quantity hfg is also called latent heat (latent = hidden) because we are unable to sense the change during this period.

Condition of the fluid at different states The fluid which has its state between ‘0’ and ‘f’ is called sub-cooled liquid, the

fluid which has its state between ‘f’ and ‘g’ is called wet steam, and the fluid which has its state beyond ‘g’ is called super-heated steam.

The boiling process starts at ‘f’ and ends at ‘g’. At ‘f’ we have 1kg of water and no vapour, similarly, at ‘g’ we have 1 kg of steam and no water. In between ‘f’ and ‘g’ we have a mixture of water and steam and this mixture is called wet steam. The ratio of

the mass of steam present in the mixture to the total mass of the mixture is called the dryness fraction denoted by ‘x’.

Dryness fraction, x = mg / (mf + mg)

Where, mf = mass of water in the mixture.

mg = mass of steam in the mixture.

(mf + mg) = total mass of the mixture. The steam, which is super-heated, has its temperature above the saturation

temperature. The amount by which the temperature is raised above the saturation temperature is called the degree of superheat.


Degree of superheat, T = Tsup - Tsat

Where, Tsat = saturation temperature

Tsup = superheated temperature.

1.12 Properties of steam at different states We can calculate some of the important properties of steam such as enthalpy,

specific volume and internal energy when the steam exists in wet state and superheated state. To do this, we need to know the values of the properties at ‘f’ and ‘g’.

Fig. 13

1.12.1 Enthalpy: Enthalpy of wet steam with dryness fraction ‘x’: We know that enthalpy is the amount of heat added at constant pressure. Therefore,

hA = amount of heat added from ‘0’ to ‘A’. = amount of heat added from ‘0’ to ‘f’ + amount of heat added from ‘f’ to ‘A’. = hf + amount of heat added from ‘f’ to ‘A’.

A dryness fraction of ‘x’ means that out of 1 kg of water initially taken, x kg is converted into steam, and (1-x) kg still remains as water.

Amount of heat added to convert

1 kg saturated water into steam = hfg Therefore,

Amount of heat added to convert

x kg saturated water into steam = x.hfg and,

hA = hf + x.hfg.

Enthalpy of superheated steam: In the superheated region steam obeys the ideal gas equation very closely. We can calculate the properties of steam in this region using the ideal gas equation.


hB = amount of heat added from ‘0’ to ‘B’. = amount of heat added from ‘0’ to ‘g’ + amount of heat added from ‘g’ to ‘B’.

hB = hg + Cps ( T) Where Cps = Specific heat of steam

T = Degree of superheat = (Tsup – Tsat)

1.12.2 Specific Volume: Specific volume is the volume occupied by unit mass of a

substance Let vf = volume occupied by 1 kg of saturated liquid

vg = volume occupied by 1 kg of saturated vapor

Specific volume of wet steam vA with dryness fraction (x)

We have taken 1 kg of water at 0o C initially. The total mass of the mixture at any state

is 1 kg. When the dryness fraction of steam is x, we have x kg of steam and (1 – x) kg of water.

Volume occupied by (1 – x) kg of water = (1 – x) vf Volume occupied by x kg of steam = x vg

Therefore, total volume occupied by the mixture

is vA = (1 – x) vf + x vg

But the specific volume of saturated water (vf) is negligible compared to the

specific volume of saturated vapour (vg). Neglecting the first term the specific volume of the mixture is approximately and very closely given by

vA = x vg

Specific volume of superheated steam (vB) In superheated region at low pressures, steam obeys the ideal gas equation very

closely. We can approximate the properties in this region using ideal gas equation.

We know that steam behaves like an ideal gas in the superheated region. Applying the ideal gas equation at states ‘g’and ‘B’ we have

pvg = RTsat pvB = RTsup

dividing, vB . = Tsup . Vg Tsat

vB . = Tsup .Vg Tsat


1.12.3 Internal energy (u) All forms of energy possessed by the system, except the kinetic and potential

energies, are collectively called as internal energy. Total energy content of the system,

Energy = Internal energy (u) + Kinetic energy + Potential energy.

By definition, enthalpy,

h = u + pv

therefore, internal energy,

u = h – pv We can calculate the internal energy of the system at any given state by

substituting the values of h, p and v corresponding to that state. Internal energy of saturated liquid,

uf = hf –pvf Internal energy of saturated vapour,

ug = hg –pvg Internal energy of wet steam,

uA = hA –pvA Internal energy of superheated steam,

uB = hB –pvB

1.4 Steam boilers The steam boiler may be defined as a closed vessel which is used to convert

water into steam at required temperature and pressure by the application of heat. The fuel used in boiler may be solid, liquid or gas. The fuel is burnt in a furnace to

produce heat. This heat is used to convert water in to steam at required temperature and pressure.

Classification of a boiler: The may be classified as follows

1) Horizontal, vertical or inclined If the axis of the boiler is horizontal is known as horizontal. If the axis of the

boiler is vertical is known as vertical boiler. If the axis of the boiler is inclines is known

as inclined boiler. 2) Fire tube boiler & water tube boiler

Fire tube boiler: In fire tube boiler the hot gases flows inside the tube and the water surrounds the tube.

Water tube

Hot gases


Water tube boiler: In water tube boiler the water flows inside the tube and the hot gases flows around the tube.

Hot gases

Tube

Water

3) Internally fired & externally fired boiler Internally fired boiler: If the furnace is located inside the boiler shell is known as

internally fire boiler. Externally fired boiler: If the furnace is located outside the boiler shell is known

as externally fired boiler.

4) Forced circulation & natural circulation Forced circulation: In forced circulation boiler, the water is circulated in the

boiler is done with the help of pump in known as forced circulation. Natural circulation: In natural circulation boiler, the water is circulated in the

boiler is due to convection currents is known as natural circulation boiler.

5) High pressure boiler & low pressure boiler High-pressure boiler: The high-pressure boiler is designed to produce steam at

very high pressure is known as high-pressure boiler. Low-pressure boiler: The low-pressure boiler is designed to produce steam at

low pressure is known as low-pressure boiler.

6) Single tube & multi tube boiler Single tube boiler: If the boiler contains only one fire tube is known as single

tube boiler. Multi tube boiler: If the boiler contains more than one fire tube is known as multi

tube boiler.

7) Stationary & portable (locomotive) boiler Stationary boiler: If the boiler is located at factory site Example, power

generation plant and the boiler used in textile mills are known as stationary boiler. Portable boiler: Portable boiler is a small boiler, which can be used as a

locomotive or temporarily used at factory sites.


1.5.1 Lancashire boiler The Lancashire boiler is a horizontal axis, fire tube, multi tubular, low pressure,

natural circulation, internally fired, and stationary boiler. The parts of Lancashire boiler are flue tubes, safety valve, steam stop valve,

pressure gauge, furnace, feed check valve, man hole, water level indicator, fusible plug

and blow off valve. Figure 14.a and 14.b shows the Lancashire boiler.

Fig14.a Lancashire boiler


Fig14.b Lancashire boiler

Construction: The Lancashire boiler consists of cylindrical metallic shell Carries

two flue tubes. Furnace is located in the flue tubes. The boiler is mounted on the brick

structure, which contains passages for the circulation of flue gases. The hot gases flows

from furnace to the other end of the tube, where the gases are made to flow in the bottom

central channel (gases run from right to the left) and reaches the left hand side of the

bottom central channel, now the gases divides in to two streams, one stream enters the

side channel-1, and the other stream enters the side channel-2, now both the streams will

runs through (right hand side to the left hand side) sides of the boiler shell and reaches

the other side of the side channels, from there it makes its last part of journey to the

chimney. Working: The furnace door is opened and charging of the furnace is done. Once

the combustion starts in the furnace it releases the heat energy, these hot gases first flows

in the flue tubes transferring the heat to the flue tubes. The hot gases, which comes out

from the flue tube, still contains large amount of heat energy, hence again these gases

are deflected to the bottom central channel. In the bottom central channel again the heat

is transferred to the bottom of the boiler shell, but still it carries some quantity of heat in

it, again the hot gases are divided in to two streams and made to flow in side channel-1

& 2. In side channel-1 & 2 again the heat is transferred to the sides of the boiler shell. The heat that is transferred from hot gases to the boiler shell is given directly to

the water present in the boiler and gets converted in to steam. This steam is collected in

the steam space and is taken out through steam stop valve to run stem turbine or for any other application.

The hot gases start its journey from the furnace and travel in several channels and

reach the chimney. Near the chimney economizer and air pre-heater is installed and

these systems will take away all the heat that is present in the hot gases. Now the hot gas

aches the chimney will have very low temperature (little more than atmospheric

temperature).

1.5.2 Babcock & Wilcox boiler Babcock & Wilcox boiler is horizontal boiler, multi tube, externally fired, water tube, stationary, low-pressure boiler and natural circulation boiler.


The parts of Lancashire boiler are flue tubes, safety valve, steam stop valve, pressure gauge, furnace, feed check valve, man hole, water level indicator, fusible plug and blow off valve. Figure 15.a and 15.b shows the Babcock & Wilcox boiler.

The parts of Lancashire boiler are flue tubes, safety valve, steam stop valve, pressure gauge, furnace, feed check valve, man hole, water level indicator, fusible plug and blow off valve.

Fig. 15.a Babcock & Wilcox boiler


Fig15.b Babcock & Wilcox boiler Construction: The Babcock & Wilcox boiler is externally fired boiler. The furnace is located at the bottom of the boiler shell. Above the furnace the water tubes are placed

and is inclined at 15o. The water flows from the boiler to down take header and flows

through pipes reaches up take header and flows back to the boiler. The flow of water is purely due to convective currents. The super heater tubes are located above the furnace.

Working: The furnace door is opened and charging of the furnace is done. Once

the combustion starts in the furnace it releases the heat energy, The hot gases rises from

the furnace and heat is transferred to both tubes and boiler shell. The boiler shell deflects

the hot gases to move downwards. The boiler shell and the baffle plate deflects the hot

gases to circulate up and down several times, there by transferring the heat to both tubes

and boiler shell. The circulation of water in the tubes is due to density difference. The steam that is collected in the steam space is known as wet steam, to convert

this wet steam in to super-heated steam, the wet steam is passed through super heater tubes. The super heater tubes are located near the furnace where the temperature is

maximum. Once the steam is converted in to super-heated steam. It goes to steam stop valve and further it goes to the application.

1.5.3 Boiler mountings: The boiler mountings are necessary for the proper function & safety of a boiler;

The various boiler mountings are listed below. i) Safety valve

ii) Water level indicator

iii) Pressure gauge

iv) Blow off valve

v) Steam stop valve

vi) Feed check valve

vii) Man hole


i) Safety valve : The boiler is designed for a pressure, but the working pressure of a

boiler is always less than the design pressure. The function of a safety valve is to protect the boiler from excess pressure, when the pressure inside the boiler exceeds the working

pressure, the safety valve opens and the excess pressure is released to atmosphere.

ii) Water level indicator: The function of a water level indicator is to indicate the actual

level of water in the boiler. For proper function of a boiler the water level in the boiler

has to be maintained between minimum & maximum level but, if the water level falls

less than the minimum results in rapid increase in pressure of steam leads to explosion of

a boiler. Always the water level indicator is located nearer & easily visible for the

operator.

iii) Pressure gauge: The function of a pressure gauge is to indicate the actual pressure inside the boiler. The pressure rating of a pressure gauge, which is mounted on a boiler, should be twice the working pressure of a boiler.

iv) Blow off valve: The function of a blow off valve is to drain the sediments from a boiler. This operation is carried out when the boiler is not in use. Always the blow off

valve is located at the lowest position of a boiler so that it is easy to drain the sediments

from the boiler.

v) Steam stop valve: The function of a steam stop valve is to regulate the quantity of steam that is going to the application. Always the boiler generates more steam than the

quantity of steam required for the application; hence steam stop valve regulates the flow and delivers the required quantity of steam to the application.

vi) Feed check valve: The feed check valve is a unidirectional valve; it allows the water from tank to the boiler and blocks the steam from boiler to the water tank. When the

pump is on it feeds the water to the boiler and, when the pump is off the high-pressure steam flows towards the feed check valve but it blocks the leakage of steam from boiler

to the water tank.

vii) Man hole: The boilers may be either water tube or fire tube boiler. In both the

boilers hot gases flow in or outside the tubes leaves behind some quantity of ash. This

ash deposit will reduce the heat transfer rate, which leads to decrease the efficiency of a

boiler. When the boiler is not in use a person enters the boiler through a man hole and

cleans the surfaces of the tubes.


1.5.4 Boiler accessories: Boiler accessories are auxiliary parts used in steam boilers for their proper

function and to improve the efficiency of the power plant. The various boiler accessories are listed below.

i) Super heater

ii) Economizer

iii) Air pre heater

iv) Steam separator

v) Steam trap

i) Super heater: The function of a super heater is to increase the temperature of the steam

above its saturation temperature. The steam, which is delivered from the boiler is known as wet steam, if wet steam is used for the application results in corrosion of parts and

erosion of turbine blades. The steam separator is in the form of U-tube, which is located

just above the furnace where the temperature is maximum.

ii) Economizer: The function of a economizer (heat exchanger) is used to recover the

waste heat from the gases going to chimney, this is also known as waste heat recovery system. The heat recovered from gases is used to heat the boiler feed water. The supply

of preheated water to the boiler reduces the amount of fuel required to raise water temperature from atmospheric temperature to preheated water temperature.

iii) Air pre heater: Air preheater is another heat exchanger is used to recover waste heat

from the gases. The air, which is fed to the furnace, is preheated to few degrees more than atmospheric temperature. Due to this, the amount of heat to be added to the air in

the furnace is considerably reduced.

iv) Steam separator: The function of a steam separator is used to separate the water particles present in the steam. The presence of water particles in the steam gives rise to blades erosion in turbines and corrosion of parts in steam engine.

v) Steam trap: The function of a steam trap is to drain the condensed steam

automatically from the steam pipes and steam separators without permitting any steam to escape to the application.

Outcomes: • Student has understood importance of energy resources. • Students are aware of the different types of non-renewable energy sources

Student gain the knowledge of different types of boilers and their application in industry and steam power plants


Review Questions

1. Differentiate between Renewable sources of energy & Non-renewable energy sources.

2. Explain different types fuels.

3. Explain with neat sketch solar Flat plate collector

4. Explain with neat sketch solar pond.

5. Explain the working of babcox & Wilcox boiler with neat sketch

6. Explain the working of Lancashire boiler with neat sketch

Turbines and IC Engines

Unit II Turbines and IC Engines

Objective:

• To understand basic definitions and mode of heat transfer.

• To study the basic laws governing heat transfer and derivation of governing equation.

Contents

2.1 Classification of steam turbine:

2.1.1. Principle of operation of Impulse turbine

2.1.2. Principle of operation of Parson’s turbine

2.2. Gas Turbine

2.2.1. Open cycle Gas Turbine

2.2.2. Closed cycle Gas Turbine

2.3. Water turbines

2.3.1 Classification of water turbine

2.3.2 Principle of operation of Pelton wheel

2.3.3 Principle of operation of Francis turbine

2.3.4 Principle of operation of Kaplan turbine

Steam turbines - Classification, Principle of operation of Impulse and

reaction turbines, Delaval’s turbine, Parson’s turbine. (No compounding of turbines).

Gas turbines: Classification, Working principles and Operations of

Open cycle and closed cycle gas turbines.

Water turbines- Classification, Principles and operations of Pelton

wheel, Francis turbine and Kaplan turbine

Internal Combustion Engines

Classification, I.C. Engines parts, 2 Stroke and 4 stroke Petrol

engines, 4 stroke diesel engines. P-V diagrams of Otto and Diesel

cycles. Problems on indicated power, brake power, indicated thermal

efficiency, brake thermal efficiency, mechanical efficiency, and

specific fuel consumption, [numericals on IC Engines].


12 hours

2.1 Steam turbines 2.1.1Introduction:

A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into useful mechanical work. A steam turbine is a

prime mover in which rotary motion is obtained by the gradual change of momentum of

the steam. Steam turbines are primarily used to run alternators or generators in thermal power plants. It is also used to rotate the propeller of ships through reduction gearing.

Main parts of a steam turbine:-


Nozzle: In steam turbines, normally, convergent-divergent type of nozzles is used.

When steam flows through the nozzles, there is a pressure drop, which is converted into

velocity or kinetic energy. The nozzles also guide the steam in the proper direction to strike

the blades. The nozzles are kept very close to the blades to minimize the losses.

Rotor: The rotor or runner consists of a circular disc fixed to a horizontal shaft.

Fig. 2.1 A rotor of a modern steam turbine, used in a power plant Blade : On the periphery of the rotor, a large no of blades are fixed. The steam

jet from the nozzles impinges on the surface of the blades due to which the rotor rotates. Casing: It is a steam tight steel casing which encloses the rotor, blades etc. In a

multistage turbine, the casing also accommodates the fixed blades.

2.1.2 Expansion of Steam in the Nozzle A nozzle is a passage of varying cross-section through which steam flows. Figure

shows a convergent-divergent nozzle in which the cross-sectional area of the nozzle diminishes from the entry to throat, and thereafter diverges to the exit as shown in the

figure 2.2. Steam is expanded in a nozzle to increase its kinetic energy. The high pressure and low velocity steam generated in a boiler enters the nozzle,

and as it passes between the entry and the throat, the pressure of the steam drops to a lower value. In other words, steam expands to a low pressure. This drop in pressure

reduces the enthalpy (heat content) of steam. Since there is no external work and heat transfer in the nozzle, the reduction in

the enthalpy of steam must therefore be equal to the increase in velocity (kinetic energy) of the steam. In other words, the steam performs work upon itself by accelerating itself

to a high velocity. Hence, the steam comes out of the nozzle with low pressure, and high

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velocity. Beyond the throat, the nozzle diverges to a certain length, so as to allow any incomplete expansion of the steam to take place.

Fig. 2.2 convergent-divergent nozzle

2.1.3 Classification of steam turbine:

Steam turbines can be classified in to two types:

1. Impulse Turbine (De-Laval Turbine): In impulse turbine the steam expands in nozzles and its pressure does not alter as it moves over the blades.

2. Reaction Turbine (Parson’s Turbine): In reaction turbine, the steam expands continuously as it passes over the

blades and thus there is a gradual fall in the pressure during expansion.

Turbines can also be classified based on

Basis Types

Action of steam or type of expansion Impulse turbine ( Velocity turbine)

Number of stages Single stage turbine Multi stage turbine

Type of steam flow Axial flow turbine Radial flow turbine

Steam Pressure Low pressure, Medium Pressure High pressure and mixed pressure turbines

Exit Pressure Condensing and non-condensing turbines


2.1.4 Single stage impulse turbine (De-Laval turbine).

The pressure energy is converted into velocity energy or kinetic energy by the expansion

of steam through a set of nozzles. Normally, in steam turbines, convergent-divergent nozzles are used. The kinetic energy is converted into mechanical energy with the help

of moving blades, fixed on the rotor. The rotor is connected to the output shaft. All these

parts are enclosed in a casing.

In operation, the high pressure, low velocity steam generated in a boiler is made to flow

through a convergent-divergent nozzle. As the steam passes through the nozzle,

expansion takes place and the pressure of the steam decreases. This drop in pressure of

the steam results in the increase in the velocity (kinetic energy) of steam. The change in

pressure and velocity of steam is shown in figure b.

The high velocity jet of steam coming out of the nozzle is directed towards the moving

blades of the turbine. The steam flowing over the blades undergoes a change in its

velocity and direction thereby resulting in change of momentum. The force due to the

change of momentum is the impulse force that acts in the direction normal to the blades,

thereby pushing the blade in its direction. The force acting on the blade is shown in

figure b.

This turbine is not suitable for practical purposes, since high-pressure steam expands in

one set of nozzles and get converted to very high velocity steam, due to this the rotor

will rotate at a very high speed. So in practice, multistage impulse turbines or compound turbines are used.


Fig: 2.3 single stage impulse turbine


2.1.5 Reaction turbine (Parson’s turbine) Reaction turbine was invented by Sir Charles Parson and hence widely called

Parson's turbine. The reaction turbine, as the name implies, is turned by reactive force

rather than by a direct push or impulse. In reaction turbines, the blades that project

radially from the periphery of the rotor are formed and mounted so that the spaces

between the blades will have the nozzle shape. Since these blades are mounted on the

revolving rotor, they are called moving blades. Fixed or stationary blades of the same

shape as the moving blades are fastened to the casing in which the rotor revolves. The

fixed blades guide the steam into the moving blade. A reaction turbine is moved by three

main forces: (1) the reactive force produced on the moving blades as the steam increases

in velocity as it expands through the fixed blades. (2) The reactive force produced on the

moving blades when the steam changes its direction. In operation, the high pressure, low velocity steam generated in a boiler passes over the

first row of fixed blades. The space between the fixed blades acts as nozzle due to which

the steam gets expanded to a low pressure and high velocity. The fixed blades guide the

high velocity jet of steam to move on to the moving blades. The high velocity jet of

steam now glides over the moving blades where it undergoes a change in its velocity and

direction, thereby resulting in change of momentum. This gives impulse force to the

blade and hence the rotor to rotate. Thus the kinetic energy of the steam is converted into

mechanical energy of rotation of the rotor. Pressure-velocity diagram is shown in figure


Fig.2.4a Reaction turbine


Fig.2.4b Reaction turbine

Fig.2.4c Reaction turbine


2.1.6 Difference between impulse turbine and reaction turbine

Impulse turbine Reaction turbine

Complete expansion of steam takes place Partial expansion of steam takes place in in the nozzle the fixed blades and further expansion

takes place in the moving blades.

Blades are symmetrical in shape Blades are non symmetrical in shape i.e.,

aerofoil section

The rotor runs at higher speeds. The rotor runs at relatively low speed.

The impulse turbines are used for small The reaction turbines are used in large power generation plant. power generation plant.

Less floor area is required.(small power More floor area is required.(Medium and plant) large power plant)

The pressure of steam remains constant The pressure of steam drops from inlet to from inlet to the outlet of the blade. the outlet of the blade

2.1.7 Advantages of steam turbines

Following are a few important advantages of steam turbines over other prime movers:

Steam turbines can work, at high temperatures and very high steam pressures. Hence the thermal efficiency is higher compared to other prime movers.

Steam turbines are rotary engines and hence do not have any reciprocating parts. Hence, less vibration and noise.

No wear and tear of the parts. Also lubrication is not required.

Turbine rotor can be balanced accurately.

Power generation in a steam turbine is at a uniform rate. Hence, a flywheel is not required.

Higher speeds with greater speed range is possible.

Steam turbines can take considerable over-load with only a slight reduction in its efficiency.

Steam turbine can be designed in sizes ranging from a few kW to over 1000 MW in a single unit. This enables to use steam turbi

ELEMENTS OF MECHANICAL ENGINEERING · (RBT: L1, L2 and L3) MODULE-5 Lathe: Principle Of Working of...

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