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					     ME 388 – Applied
Instrumentation Laboratory
   Centrifugal Pump Lab
                References
• Streeter and Wylie, Fluid Mechanics (Ch.10)

• Holman, Experimental Methods for Engineers,
  (Ch.6)

• Munson (Ch.9)

• Any Fluid Mechanics book
              Lab Objectives
• Understand operation of a dc motor
• Analyze fluid flow using
  – Centrifugal pump
  – Venturi flow meter
• Evaluate pump performance as a function of
  impeller (shaft) speed
  – Develop pump performance curves
  – Assess efficiencies
   Lab Set-up
Paddle meter           Valve

                                       Venturi
                                             (P)
                       Dynamometer


           E       I
                                            Pout
                                Pump
               Motor
                         T                 Pin




           Water Tank
                     dc motor

•Armature or rotor
•Commutator
•Brushes
•Axle
•Field magnet
•DC power supply




                     Figure 1. dc motor (howstuffworks.com)
           Centrifugal pump
http://www.cheresources.com/centrifugalpumps1.shtml
http://www.pumpworld.com/contents.htm
Cavitation
     Centrifugal pump operation
• Rotating impeller delivers energy to fluid

• Governing equations or Affinity Laws relate
  pump speed to:
  – Flow rate, Q
  – Pump head, Hp
  – Fluid power, P
           24
                                                                    1400                  0.6
           22

           20                                                       1200
                                                                                          0.5
           18




                                                                                            pump efficiency, 
                                                                    1000
           16




                                                                        fluid power (W)
                                                                                          0.4
           14
Head (m)




                                                                    800
           12                                                                             0.3
           10                                                       600

           8                                      operating point                         0.2
                                                                    400
           6

           4                          pump head 1709 rpm                                  0.1
                                      fluid power 1709 rpm     200
           2                          pump efficiency 1709 rpm
                                      system load - head
           0                                                         0                    0.0
            0.000   0.002   0.004    0.006       0.008    0.010     0.012
                                             3
                               Flow Rate (m /s)
     Pump Affinity Laws
            N1 Q1
• NQ          
• N2  Hp
            N 2 Q2
• N3  P         2
             N1    H p1
            
            N   
             2     H p2
                 3
             N1    P
            
            N     1
             2     P2
 Determination of Pump Head

     Pout  Pin V22  V12
Hp                       Z 2  Z1
        g         2g


              Pout  Pin
         Hp 
                 g
     Determination of Flow Rate
• Use Venturi meter to determine Q

• Fluid is incompressible (const.  )
  Q = Vfluid Area
               Venturi Meter




•   As V , kinetic energy 
•   T = 0
•    Height = 0
•   Pv or P 
     Calculate Q from Venturi data

                Q  C d A2V2
•   V1 = inlet velocity
•   V2 = throat velocity
•   A1 = inlet area
•   A2 = throat area
           Throat Velocity
      2             2
    V1    P1  Z  V2  P2  Z
               1              2
    2g     g          2g       g
                  A2        2        P  P  P2
Z  0    V1  V2     V2 B                1
                  A1
            .    .          
            m1  m 2  A v

         V2  f (P, B,  )
      Discharge Coefficient

                   B           D2
Cd  0.907  6.53           B
                  ReD          D1

        V1 D1
ReD   
                           A2
                    V1  V2     V2 B 2
                            A1
                Solve for Q
• Use MS EXCEL (or Matlab)
• Calculate throat velocity
• Calculate discharge coefficient using
  Reynold’s number and throat velocity
• Calculate throat area
• Solve for Q
      Power and Pump Efficiency
• Assumptions
  –   
      Q0
  –   No change in elevation
  –   No change in pipe diameter
  –   Incompressible fluid
  –   T = 0
• Consider 1st Law (as a rate eqn.)

  W  m h  h   1 V 2  V 2  g Z  Z 
Q   2 1
                     2
                         2    1       2   1 
                                              
       Pump Power Derivation
h  u  Pv
W  mh2  h1   mu2  P2v   u1  P v 
                                      1

W  mvP2  P 
  
             1
      
mv  AV  Q



         W  Q P  P 
                  2   1
         Efficiencies
           output QP2  P 
 pump                   1
            input       T
           T
 motor 
            EI
             QP2  P 
 overall           1
                EI
     Summary of Lab Requirements
•   Plots relating Hp, P, and pump to Q
•   Plot relating P to pump
•   Regression analyses
•   Uncertainty of overall (requires unc. of Q)
•   Compare Hp, P, Q for two N’s
    – For fully open valve position
    – WRT affinity laws
                                   905 rpm
                                   1099 rpm
                                   1303 rpm
                                   1508 rpm
                                   1709 rpm
Pump Head (m)




                            3
                Flow Rate (m /s)
                               905 rpm
                               1099 rpm
                               1303 rpm
Power Delevered to Fluid (W)


                               1508 rpm
                               1709 rpm




                                                      3
                                          Flow Rate (m /s)
                  905 rpm
                  1099 rpm
                  1303 rpm
                  1508 rpm
                  1709 rpm
pump efficiency




                                         3
                             Flow Rate (m /s)
Pump Efficiency




                                         905 rpm
                                         1099 rpm
                                         1303 rpm
                                         1508 rpm
                                         1709 rpm




                  pump power delivered to fluid (W)
                Start-up Procedure
1.    Fill pvc tube with water (3/4 full)
2.    Bleed pump
3.    Switch breaker to “on”
4.    Push main start button
5.    Make sure variac is turned counterclockwise
6.    Make sure throttle valve is fully open
7.    Turn lever to “pump”
8.    Push “reset” button
9.    Push “start” button
10.   Adjust variac to desired rpm using tach.
                  Pump lab raw data
Shaft   DC         DC        Inlet      Outlet     Venturi DP   Dyna
speed   voltage    current   Pressure   Pressure   (kPa)        (lbs)
(rpm)   (volts)    (amps)    (in Hg)    (kPa)
          Shut-down Procedure

1.   Fully open throttle valve
2.   Turn variac fully counterclockwise
3.   Push pump stop button
4.   Turn pump lever to “off”
5.   Push main stop button
6.   Switch breaker to “off”

				
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