ME 388

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ME 388 Applied Instrumentation
LaboratoryCentrifugal Pump Lab
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References

• Streeter and Wylie, Fluid Mechanics (Ch.10)
• Holman, Experimental Methods for Engineers,
  (Ch.6)
• Munson (Ch.9)
• Any Fluid Mechanics book

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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

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Lab Set-up
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dc motor

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

Figure 1. dc motor (howstuffworks.com)
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http//www.cheresources.com/centrifugalpumps1.shtm
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Centrifugal pump
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http//www.pumpworld.com/contents.htm
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Cavitation
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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

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Pump Affinity Laws

• N ? Q
• N2 ? Hp
• N3 ? P

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Determination of Pump Head
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Determination of Flow Rate

• Use Venturi meter to determine Q
• Fluid is incompressible (const. ? )
• Q Vfluid Area

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Venturi Meter

• As V ?, kinetic energy ?
• ?T 0
• ? Height 0
• ?Pv or P ?

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Calculate Q from Venturi data

• V1 inlet velocity
• V2 throat velocity
• A1 inlet area
• A2 throat area

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Throat Velocity
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Discharge Coefficient
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Solve for Q

• Use MS EXCEL (or Matlab)
• Calculate throat velocity
• Calculate discharge coefficient using Reynolds
  number and throat velocity
• Calculate throat area
• Solve for Q

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Power and Pump Efficiency

• Assumptions
• No change in elevation
• No change in pipe diameter
• Incompressible fluid
• ?T 0
• Consider 1st Law (as a rate eqn.)

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Pump Power Derivation
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Efficiencies
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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 Ns
• For fully open valve position
• WRT affinity laws

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Start-up Procedure

• Fill pvc tube with water (3/4 full)
• Bleed pump
• Switch breaker to on
• Push main start button
• Make sure variac is turned counterclockwise
• Make sure throttle valve is fully open
• Turn lever to pump
• Push reset button
• Push start button
• Adjust variac to desired rpm using tach.

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Pump lab raw data
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Shut-down Procedure

• Fully open throttle valve
• Turn variac fully counterclockwise
• Push pump stop button
• Turn pump lever to off
• Push main stop button
• Switch breaker to off