EMB Centrifugal Pump

8/12/2019 EMB Centrifugal Pump

1/9

EMB 5443FACILITIES ENG. TRANSPORTATION

LABORATORY MANUAL SHEET

CENTRIFUGAL PUMP


2/9

1.0. OBJECTIVEi. To investigate the relationship between Pressure Head, Flow Rate, Power

consume and Efficiency for centrifugal pump.2.0. INTRODUCTIONThe use of the design of hydraulic machinery is important to many engineering tasks.Hydraulic machinery can be broadly divided in two classes: pumps and turbines. A pumpconverts mechanical or electrical energy from an out side source in to hydraulic energy,often in the form of a pressure rise. Many of the hydraulic machines use in engineeringapplications are centrifugal pumps, where an essential part of the machine is a rotatingmember. This member is called an impeller. Centrifugal pumps are frequently used in alocation where they are place above the level of the supply fluid.2.I. BASIC PRINCIPLECentrifugal pump has a shrouded running on an extension of the main spindle, supportedon double ball bearings. This type of pump is not self-priming but operates with a floodedsuction. Its single impeller rotates in the snail-shaped voluted casing. Water enters theimpeller circumference in to the casing (seeFigure 1).

Xlgura l. Ccntitugel Prmp

As the fluid passes though the impeller, energy is imparted to it by the curved blade ofthe impeller resulting in fluid leaving the impeller with an increase of pressure andvelocity.


3/9

The pump has a suction connected to the sump tank via a suction regulator valve. Itsdelivery is connectEd to the selection manifold and measuring system via a globe v.alve.v@ffi,6- g

(1.1)

,..............(1.2)

q : Pump hydraulic fficiencySP : shaft power / input power, wattsW : water power / hydraulic power, wattsp : Density of water, kg / m3g: gravity, m /s2Q: rte offlow, *3 / sH: pump head, m. HzoN: motor speed, rev / minT: torque, N.m

Peak pump efficiencies typically range from 0.5-0.9 for centrifugal pumps. These pumpsare used when relatively large heads and low flow rates are desired.

When a pump is putunder test the usual objective is the determination of its characteristic curves. Thesecurvos

Figure 2).

The

Where:


4/9

Dtdtergr0owFfgsrc ?- Typicat Chsrdaistic Clnves fu Ceutrifirgal Purq

2.2. THEORYCentrifugal pumps are capable of transferring large volumes without any dependence onvalves or fine clearance and can be run against a closed valve with out develop in a veryhigh pressure. They can handle a wide range of slurries, or solids in suspension, inaddition to liquids with high viscosities.

A centrifugal pump must generally first be primed. That is, the pump casing and supplyline are first filled with the fluid to be used, to remove all air. The check valve insuresthat this fluid stays in the pump. In some installations a given pump can be self-priming.An expression for the theoretical torque ended to drive a centrifugal pump can be foundby considering the velocity diagrams and control volume (see figure 3). Let I and 2denote inlet and out let conditions, respectively, where the fluid enters at the smaller ofthe two radii, 11. The various velocity components are as given in TABLE 1.

lnlet velocity components Outlet velocity componentsTangential Normal Tangential NormalAbsoluteRelative

V1 COSO(1 V1 sincr,V1 cosO(, -r1C) V1 sincr, V2 coSO(, V2 sinCf ,V2 cosO(r-r2C) V2 sinU,

Table 1. Centrifugal pump velocity components


5/9

With an impeller having a passage of uniform height w, the normal velocity componentsare related to discharge according to

Q=2nrrVrsinot,, = 2nrrVrsincxr........ ...........(1.4)Figure 3. Centrifugal Pump Impeller Velocities

We will consider only the case where the flow enters and exits tangent to each vane ofthe impeller. For this case the vane slope is the same as the slope of the velocitycomponent. Thus the ideal entering and exiting vane angles p, and B, are given by

tanB, -vrcosur/ ,/ (rr{2- Z, coscr, )and .0.5)/. n V" COSA" /ran9z = ' furt)_Vrcosar)

Having the flow enter tangentially to the vane ensures that there is no momentum lossnormal to the impeller. Other angles will result in inlet losses.The head delivered to the fluid in passing through the pump is, by the energy equation,

Normally the greater portion of head delivered is due to the pressure rise, since the entryand outlet areas are nearly equal.The ideal torque applied to the pump (the torque needed if there were no losses) is themass rate of flow times the moment of momentum changes. This involves only thetangential components of the entering and exiting velocities. Thus

Tid"ot=pQ?rZrcosc[2-rrVrcosa,,) ............. ..................0.7)Notice that the ideal torque can be maximized by having the fluid enters the impellernormally (cr,:90).


6/9

3.0. EXPERIMENTALPROCEDURE3.1. BASIC PRINCIPLEThe schematic diagram of the experiment set-up of multi-pump test rig for centrifugalpump is shown in Figure 4. The centrifugal pump comprises of the followinecomponents:

lts+,,t55A.,6,'?tr

4itoItli'l{ll'tft7.tlItrloEE

'1{:t

fisC4'ikErGwgnrgpA&lrlnpsrtCotjrug.lpuptu6iorpuag$lrraaiurirmtx.qilrE$rtEcbryl6.a"sqlrbhedcl{o**pturlrgr .lrdrd.ild'ld.liU *id.ct6fdrrFfry setrol rilnA$rt o/.pn urfdrlm$sif,rrtuhd|'rdr|.lilnlc'Fc4cFtil&tdg*r-'frc*igBt6Yru,trnr3th.Flr.rffii u$.'*lrnls$r|P'lulDffip$fFtoolbc4blt

nqffitbUmg*mpJttorlmpmtftc-a6rt&;t,{ddthttA-Dnln

Figurr 4. Multi-fury Test Rig Oplratine Instucrier Diagram

3.2. EXPERIMENTAL PROCEDURELearning outcomes:You will be able to determine the centrifugal pump characteristic curves.Procedures:

6

3E


7/9

a) Fill the sump tank with clean water to 50 mm from the topb) Close flow control valvec) Open suction regulating valved) Set motor speed control to zeroe) Ensure that the dynamometer motor torque arm has been correctly set to zero0 Switch on motor and rotate the motor speed controller clockwise to give

required rev/min. Allow he motor to run for 5 (five) minutes to warm upg) Open flow control valve and set it, and the suction regulating valve to give therequired rate of flow (select six different rate of flow)

h) Measure the rate of flow using the graduated sight glass on the volumekic tankand the stopwatch, do it 3 (three) times to get to,",os.

D Pressure readings for the centrifugal pump are taken from pressure gaugesj) Vacuum readings are taken from vacuum gaugek) Record the torque reading at each flow rate1) Tabulate this data in the results tablem) Repeat operations (c) to (k) for two other motor speeds

4.0. RESULT A]\D DISCUSSION4.I. RESULTTable-l: DataMotor speed: ..l.:4.?. ........rev /minReading Pressure(m.H2o)

Vacuum(m.Hzo)

Pump Head(m.H2o)

Volume(ltr)

Time(sec)

Flow(*ttt)

TorqueOr.m)

InputPower0Yattl

HydraulicPowerQrat9

Effrciency(q)

I ,.4661 3 qtgq r0 2t U qJo15? 0t 1f 'f' lb.t4J AtN2 i-?33: o 2.'t33) t0 {Y

u-\rou?t tlJ o

-5"J 2 qm'l O t t{qo* 10 lr r)'*N4',)'1N o'\f;456


8/9

891011

Table-2:Motor speed:

Dataprn

4 cso76b\oli0t\zo\'fi@

4.2. DISCUSSIONUsing the data obtained, determine the most efficient operating point for thepump at a given pump speedUnder what particular set of conditions was the pump under test operating at itshighest efficiency? Explain whyFrom the data from the result table, plot graph flow rate, Q vs. pressure head, H,flow rate, Q vs. input power, SP, and flow rate, Q vs. efficiency, q .Referring to the power/low graph, should the pump under test be started with its

a)

b)

c)

d) \/\,I1rtrtJ

\

Reading Pressure(m.Hzo)Vacuum(m.H2o)

Pump Head(m.H2o)

Volumeaft)

Time(sec)

Flow(*ttt)

Torque(I,l.m)

InputPower(lYatt0

HydraulicPowerlVattl

Efficiency(q)

1 25 0 o'82 + t1, o.Qen.A9]2 z1 ,{ o l 4 t6 +.&f.l.orhaJ gt.9 o r-t "i rqIJ l,o2T4 33 1 o I t'\t./ v t3 i,t35 31 \ o tt( 7 l.\ t.gq6 31 "3 o l-6 7 to t 33891011

flow valve open or closed? Explain why


9/9

e) Which is better NPSHu.6u1 > NPsH..quireo or NPSHactual ( NPSHr"q,r;."a? Explainwhy

0 State three suitable industrial applications for the type of pump under tes.Correlate the industrial application with the test data obtained.

Format of the report:1. Write, in the front cover page

Title of the Experiment, Course number and course title, Name of instructor,Group Number, Name of Student, Test date, Submission Date,

2. Objective of the exercise- Specifli, in short, the aim of the experiment.3. Instrumentation- List the instruments used during the experiment including the accuracy

and make of the instruments.4. Procedure for the experiment- Discuss how the set up is arranged and the procedures followed during the

experiment.5. Data

a. Given datab. Data collected during the experiment and calculated values.6. Discussion- Discuss and tabulate the required values in section 4.2.7. Conclusion

Note: The lab. Report should be submitted within one week after the experiment.

5.0. REFERENCES1. Graebel, W.P., Engineering Fluid Mechanics, Taylor & Francis Publishers, 20012. Multi-Pump Test Rig Instruction Manual, Armfield Limited, 1999.

9

Documents

EMB Centrifugal Pump