ENG211 Fluid Mechanics 2016: Practical 4 – Pump Curves (Mark 5%)
Individual reports required from each student.
(Note: You may need to learn the theory in the workshop before you will fully understand this prac!).
AIM:
To investigate the effects of varying the flowrate and motor speed on pump performance curves.
THEORY:
In this weeks workshop you will learn about the operation of centrifugal pumps. You will learn what pump performance curves are, what pump efficiency means and how to calculate pump power requirements for pumping systems. This practical is designed to give you a better understanding of how real pumping systems operate.
In this practical you will use the pump testing apparatus to develop pump performance curves for a swimming pool pump (and pump test unit) operating at three different speeds. You will measure the flowrate, pressure head and actual power requirements over a variety of flowrates (from Qmax to Q=0) to develop these curves. You will then calculate the theoretical power requirements for the flowrates and pressure heads and compare these to make an estimation of the best efficiency point for the pump at each speed. The theoretical Power required for ideal flow conditions is calculated using Equation 1:
WP = ?gQhP (Eq. 1)
PROCEDURE:
1. Make sure that the pump is plugged into the Futurewave Unit and set the Controller to 50Hz;
2. Make sure the control valve is fully opened and turn the pump on;
3. Record the maximum flowrate (Qmax), inlet pressure (P1), outlet pressure (P2), and power reading (W) when the valve is fully open;
4. Using Qmax, calculate flowrates in increments of 10% reductions as shown in Table 1 (e.g. 0.9Q);
5. By closing the control valve, adjust the flowrate to be as close as possible to the next flowrate increment (e.g. 0.9Q), then record inlet pressure (P1), outlet pressure (P2), and power reading (W) for this flowrate (you should notice that the outlet pressure increases greatly);
6. Repeat step 5 for all other flowrates down to Q = 0;
7. Once you have all the readings for the first test, fully open up the control valve again;
8. Adjust the Futurewave Controller and set the cycle time to 40Hz;
9. Repeat Steps 2 - 6 for the 40Hz test;
10. Once you have all the readings for the second test, fully open up the control valve again;
11. Adjust the Futurewave Controller and set the cycle time to 30Hz;
12. Repeat Steps 2 - 6 for the 30Hz test;
13. Fully open up the control valve again and turn pump off.
So after completing these measurements, you should have three sets of data for this experiment.
RESULTS
Table 1 – Measurements for XXX ???W Motor at 50Hz (2800RPM)
Qmax 0.9Q 0.8Q 0.7Q 0.6Q 0.5Q 0.4Q 0.3Q 0.2Q 0.1Q Q=0
P1
(kPa)
P2 (kPa)
Power (W)
Table 2 – Measurements for XXX ???W Motor at 40Hz (~1960RPM)
Qmax 0.9Q 0.8Q 0.7Q 0.6Q 0.5Q 0.4Q 0.3Q 0.2Q 0.1Q Q=0
P1
(kPa)
P2 (kPa)
Power (W)
Table 3 – Measurements for XXX ???W Motor at 40Hz (~1120RPM)
Qmax 0.9Q 0.8Q 0.7Q 0.6Q 0.5Q 0.4Q 0.3Q 0.2Q 0.1Q Q=0
P1
(kPa)
P2 (kPa)
Power (W)
REPORT
The idea of this practical is to generate performance curves for the pump for the three different motor speeds (50Hz, 40Hz and 30Hz). Using EXCEL and your results from Tables 1 - 3, calculate the differential head (P2P1) for each flowrate in meters. Then calculate the theoretical pump Power (WP) required to lift the flowrate to that differential head. Using the calculated values, generate performance curves for each motor speed
The theoretical power curve shown in Figure 1 can be used in place of an efficiency curve for the pump. Locate the maximum efficiency point on your theoretical power curves and estimate the flowrate and differential head at that point (equals approximately Q= 3.1L/s and hP = 9.5m on Figure 1). Then calculate the pump efficiency (?) at that point by dividing the Theoretical Power by the Actual Power (? = approx. 0.33 on Figure 1). Repeat these calculations for all three pump speeds to find the best efficiency flowrates and head for the pump at the three speeds.
Discuss your pump performance results and the possible reasons for any large discrepancies in the results.
Please submit a brief written report including the aim, method, results graphs, discussion of the above tasks and conclusion (see: Engineering Practical Report Guidelines 2016 in Learning Materials folder).
Submit hardcopy of report to me in the Week 12 Workshop.