APPENDIX G – Pumps and Turbines
Surge Analysis and the Wave Plan Method
Supplementary Material: Example Problems and Solutions
Appendix G – Problem 35
G.35 A pump station with 3 identical pumps described in the previous example (7.5 m3/s flowrate) is tripped due to power outage. Five seconds after the pump trip event, a tachometer attached to one of the pumps shows a speed of -300 rpm and a flowmeter attached to the same pump read -3.3 m3/s.
a. Compute the corresponding pressure head and torque values assuming the pump adheres to the standard non-dimensional characteristics shown in Figures G.14 through G.17 during a trip.
b. What is the corresponding zone of operation and Karman-Knapp quadrant?
c. If the combined moment of inertia (of the pump and motor) for each pump is 35000 Nm2, compute the pump speed at a computational time step of 0.001s at time 5.001s after the trip. [Hint: Use Eq. G.7 with appropriate value for torque at time 5s after the trip].
d. Repeat part (c) with computational time steps 0.002s, 0.005s, 0.01s and 0.05s.
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