articol jmse

7/30/2019 articol jmse

1/5

Journal of Materials Science and Engineering A 2 (3) (2012) 372-376

Research Regarding the Testing of a New Type of

Rotating Machine with Profi led Rotors

Nicolae Bran, Ionela Mihaela Cluaru and Antonios Detzortzis

Faculty of Mechanical and Mechatronics Engineering, POLITEHNICA University of Bucharest, CO 060042, Romania

Received: January 18, 2012 / Accepted: February 15, 2012 / Published: March 10, 2012.

Abstract: The purpose of the research is to theoretically establish the simple characteristic diagrams of the rotating machine and to

verify them by experiments. In order to reach this goal, the scheme of an experimental setup was elaborated, as well as its constructive

solution. The final part of the paper presents the method of the measurements to be performed. The experimental data are processed and

compared to the theoretical ones.

Key words: Rotating machine, profiled rotors, rotating piston.

1. Introduction

The machine is in fact a patent-based rotating

volumetric pump [1]; the paper will highlight the

influence of constructive and functional parameters on

the theoretical power of the machine.

This type of rotating machine is reversible,

meaning that it can function as working machine

(pump, fan or blower) or as force machine (hydraulic

motor, steam motor or burning gas motor) [2-4]. When

the machine is used as working machine, the motor

torqueM = Fbsin reaches its maximum value during

a complete rotation, because the angle () between the

force (F) and the arm (b) equals 90.

The motor torque is almost fully used for increasing

the fluid pressure from intake (p1) to discharge (p2). If

the machine is used as force machine, p1 > p2 and

mechanical power that could be converted to electric

power are obtained at the machine shaft level.

In the following sections, the rotating machine will

be studied as working machine, namely as rotating

volumetric pump with profiled rotors.

Corresponding author: Nicolae Bran, Ph.D., professor,research field: working machines. E-mail:

[email protected].

2. Computation of the Fluid Flow Rate and of

the Theoretical Driving Power for the

Rotating Volumetric Pump

The machine consists (Fig. 1) of two identical rotors

(2, 5) of special shape, which rotate with the same

angular speed inside a casing (1,4). The fluid contained

in the available volume Vu, which is the space between

the pistons, the lower casing (1) and the lower rotor (2),

will be transported to the discharge chamber after a

180 rotation. Two such volumes will be transported

from intake to discharge during a complete rotation of

the shaft (9):2 2

3c ru

R RV 2 l(m /rot)

2 2

(1)

The casing radius (Rc) is computed as sum of the

rotor radius (Rr) and of the piston height (z):

Rc = Rr+ z (m) (2)Eqs. (1) and (2) lead to:

3

u rV lz(z 2 R )(m /rot)

(3)

The volumetric flow rate discharged by a sole rotor

of length l(m) and angular speed n (rpm) will be equal

to:

3u rn

V lz z 2R (m /rot)60

(4)

Because the machine has two identical rotors, the

DAVID PUBLISHING

D


2/5

Research Regarding the Testing of a New Type of Rotating Machine with Profiled Rotors 373

Fig. 1 The functioning principle of the rotating volumetric

machine.

1-lower casing; 2-lower rotor; 3-intake chamber; 4-upper casing;

5-upper rotor ;6-rotating piston; 7-driven shaft; 8-discharge

chamber; 9-driving shaft ; 10-cavity where the piston of the

upper rotor enters.

fluid flow rate transported by the machine will be equal

to:

( )

.

3

m u r

nV 2V lz z 2R (m /s)

30

= = + (5)

It can be noticed from Eq. (5) that the machine flow

rate linearly increases with l, Rrand n.

For a total increase of pressure (between intake and

discharge) expressed using p (N/m2) orH [mH2O],

the theoretical power (Pm) needed in order to drive the

machine will be equal to:

( )m rn

P lz 2R z p(w)30

= +

(6)

( )2m r H O

nP lz 2R z g H(w)

30= +

(7)

It can be noticed from Eq. (6) that the driving power

of the machine is directly proportional to the

constructive elements (l, Rr, z), to the angular speed (n)

and to the pumping speed (H).

3. Theoretic Establishment of SomeCharacteristic Diagrams of the Working

Rotating Machine

In continuation it is considered that the working

machine will function as rotating volumetric pump. It

is known from specialty Refs. [5, 6] that the pumps

classify in two categories:

I-Non-volumetric pumps (for instance the

centrifugal pump, the axial pump);

II-Volumetric pumps (for instance the gear pump,

the pump with profiled rotors etc.).

For the new type of machine, starting from the

relations previously established for flow rate (5) and

for power (6), we notice that the following theoretical

characteristic diagrams can be built:

(1) mV f (n )

= ; if the discharge pressure is kept

constant, a line is obtained. Another line is

subsequently obtained if the discharge pressure is

modified.

(2) mP f ( p)= ; a line is obtained if the angular

speed is kept constant n = ct. If the angular speed is

subsequently modified, the flow rate will be also

modified, as well asPm.

For the chosen constructive solution [7, 8] and built

in the laboratory the following parameters are known:

Rotor length: l = 0.05 m; Height of the rotating piston:z = 0.03 m; Rotor radius:Rr= 0.05 m; Motor speed can be modified in the range of

200-300 rpm; if the motor speed is increased over 300

rpm, the water speed at intake increases over 0.89 m/s,

that is not recommended in the specialty literature[5, 9].

In order to build the theoretical characteristic

diagram mV f (n)

= , the computation formula for the

flow rate is rearranged in the following equation:

3m

nV 0.05 0.03(0.03 2 0.05) (m / s)

30

= + (8)

3 3mV 0.020 4 10 n (m / s)

= (9)

The following values are chosen: n = 200, 220, 240,

260, 280 and 300 rpm. Data presented in Table 1

results that Eq. (9) is applied to these values.

The obtained data is used to obtain the characteristic

diagram mV f (n)

= .

In Fig. 2, mV

denotes the theoretical flow rate

transported by the machine; measurements will be

Table 1 Values of n.

n (rpm) 200 220 240 260 280 300

mV

(l/min)

244.92 269.41 293.90 318.39 342.88 367.38


3/5

Research Regarding the Testing of a New Type of Rotating Machine with Profiled Rotors374

Fig. 2 The theoretical characteristic diagram of the

machine: mV f (n )

performed in order to establish the real flow rate ( rV

)

of the fluid.

It can be thus computed the volumetric efficiency of

the machine:

rv

t

V

V

(10)

The value of v is needed for the computation of

the actual efficiency of the machine.

To establish the dependence mP f ( p) , Eq. (6)

must be written as follows:

mP V p(W)

(11)

A medium angular speed of 220 rpm is chosen. The

angular speed will remain constant during the test.

m

220P 0,05 0,03(0,03 2 0,05) p(W)

30 (12)

mP0045 (13)

where p is the pressure increase achieved by the

pump (bar).

In laboratory conditions, it is possible to obtain a

pressure increase of at most: p = 1 bar 10 mH2O. 5

points are chosen in the variation range ofp: 0.20;

0.21; 0.22; 0.23; 0.24 bar.

A medium angular speed of 220 rpm is chosen. The

angular speed will remain constant during the test. For

the first value ofp, it is obtained that :5

m,1 1P 0.0045 p 0.0045 0.2 10 90(W) (14)

The other values are similarly computed and can be

found in Table 2.

The data in Table 2 lead to the graphical representation

of the function mP f ( p) .

In Fig. 3,Pm denotes the useful power of the machine;

if the power absorbed from the line system is measured

using the wattmeter kit, the actual efficiency of the

machine can be computed.

4. Setup Description

In order to establish the characteristic diagrams of

the rotating volumetric pump, a closed circuit setup Fig.

4 wasbuild in the laboratory of the Chair of

Thermotechnics, Thermic Machines and Refrigeration

Plants. Potable water from the water supply is used as

working fluid; the level of water in the tank is indicated

by the level glass indicator (2) and is of about 1 m. The

water is suctioned from the tank (1). The increase ofpressure achieved by the pump (10) is measured using

a differential manometer (15). The flow rate is

measured with an electromagnetic flow meter (11).

The increase of pressure between intake and

discharge is modified using the ball valve (13).

The instruments collocated on the setup circuit allow

the measurement of fluid pressure, temperature and

flow rate.

The rotation speed of the electric motor and the

absorbed electric power can be as well measured and

regulated.

Table 2. Values ofp

p (bar) 0.20 0.21 0.22 0.23 0.24

Pm (W) 90.0 94.5 99.0 103.5 108.0

Fig. 3 The theoretical characteristic diagram of the

machine: mP f ( p) .


4/5

Research Regarding the Testing of a New Type of Rotating Machine with Profiled Rotors 375

Fig. 4 Sketch of the experimental setup for testing the rotating volumetric pump with profiled rotors.

1-liquid tank; 2-level glass indicator; 3-filling pipe; 4-closing valve; 5-thermometer; 6- manometer; 7-electric motor; 8-dispozitiv de

reglare a turatiei ALTIVAR 58; 9-digital manometer; 10-volumetric pump; 11-electromagnetic flow meter; 12-emptying fitting;

13-control valve; 14-discharge pipe; 15-differential manometer.

5. Method of Measurement

For the experimental establishment of the

characteristic diagram mV f (n)

, it is necessary to

perform the following operations:

(1) The tank (1) is filled with water (Fig. 4) till h 1

m; the valve collocated at the pump intake is opened.

(2) After the filling of the circuit, the pump is aerated

and its shaft is manually rotated in order to check that itis not blocked.

(3) The valve (13) is completely opened.

(4) The pump is started, its rotation speed is adjusted

to a value of n = 220 rpm and the flow rate m ,1V

that

passes through the electromagnetic flow meter is

read.

(5) The rotation speed of the pump is subsequently

adjusted to 240, 260, 280, 300 rpm; the flow rates m ,2V

,

m ,3V

, m ,4V

, m ,5V

are read. The experimental data are

processed and compared to the theoretical ones

(Table 3).

The data from Table 3 lead to the graphical

representation of the function mV f (n )

shown in

Fig. 5.

The theoretical and experimental results prove a

satisfying coincidence.

For the experimental establishment of the

characteristic diagram mP f ( p) the following steps

are needed:

The steps 1, 2 and 3 are like above.

(4) The volumetric pump is opened. The rotation

speed is adjusted to a mean value ofn = 220 rpm.

(5) Using the control valve (13), a pressure increase

of 0.2; 0.22; 0.23; 0.24 bar is established; the values of

Pm are read.

The experimental data are processed and compared

to the theoretical ones (Table 4).

Table 3 Values of mV

and rV

n (rpm) 200 220 240 260 280 300

mV

(l/min) 244.92 269.41 293.90 318.39 342.88 367.38

rV

(l/min) 233 257 281 304 332 353

Table 4 Values of Pm and Pr.

p (bar)

0.20 0.21 0.22 0.23 0.24

Pm (W) 90.0 94.5 99.0 103.5 108.0

Pr(W) 127.0 130.9 133.3 137.5 140.0


5/5

Research Regarding the Testing of a New Type of Rotating Machine with Profiled Rotors376

Fig. 5 The experimental characteristic diagram of the

machine: mV f (n )

.

Fig. 6 The experimental characteristic diagram of the

machine: mP f ( p) .

The obtained data are used to obtain the

characteristic diagram mP f ( p) .The graph shown in Fig. 6 indicates an

approximately linear increase of the power absorbed by

the machine with the pressure increase of the pump.

6. Conclusions

(1) The purpose of the researches was reached,

because a number of characteristic diagrams for this

new type of machine were experimentally built;

therewith the performed measurements allow

establishing the volumetric efficiency and the actual

efficiency of the machine.

(2) The measurement results are highly accurate due

to the fact that the instruments (thermometer,

manometer, flow meter, counter) were calibrated and

digitally displaied the measurement values.

(3) Both the rotating machine with profiled rotors

and the constructive solution of the setup are original,

fact that increases the value of the work and allows

expanding the research in the field of rotating machineswith profiled rotors.

Acknowledgments

The work has been funded by the Sectoral

Operational Programme Human Resources

Development 2007-2013 of the Romanian Ministry of

Labour, Family and Social Protection through the

Financial Agreement POSDRU/107/1.5/S/76903.

References[1] N. Bran, G. Bran, Steam rotating motor, Patent no.

111296 released by the State Office for Inventions and

Trademarks OSIM Bucharest.

[2] M. Marinescu, N. Bran, V. Radcenco, TechnicalThermodynamics, Vol. I,II,III, Matrixrom Publishing

House, Bucharest, 1998. (in Romanian)

[3] N. Bran, P. Rducanu, Bases of technicalthermodynamics, vol.3, Technical thermodynamics (in

Romanian), POLITEHNICA PRESS Publishing House,

Bucharest, 2010.

[4] A. Motorga, The Influence of Functional and ConstructiveParameters on the Performance Rotating Machines with

Profiled Rotors, Politehnica Press Publishing House,

Bucharest, 2011.

[5] M. Exarhu, V. Tcacenco, Bases of the ExperimentalResearch of Hydraulic and Pneumatic Machines,

Bucharest, 1990. (in Romanian)

[6] M. Exarhu, V. Tcacenco, Guide for the Laboratory ofHydraulic Machines, Bucharest, 1994. (in Romanian)

[7] N. Bran, D. Besnea, D. Duminic, Research onestablishing the outline of the rotor profile for a new

volumetric rotating pump, Mecatronica 4 (2004) 24-27.

[8] N. Bran, O. Donu, D. Besnea, A. Costache, Constructiveelements and technological procedures used in the

construction of a new type of rotary compressor, Romanian

Review Precision Mechanics, Optics and Mecatronics 25

(2004) 261-268.

[9] C. Iamandi, V. Petrescu, Fluid Mechanics, Didactical andPedagogical Publishing House, Bucharest, 1979. (in

Romanian).

articol jmse

Documents

Transcript of articol jmse