Sacramento State University         Dept. of Civil Engineering
CE 135 Hydraulics Lab                       Instructor      MEH

PELTON WHEEL TURBINE

Study the performance of a Pelton wheel impulse turbine.
Determine the efficiency of the turbine speed over a range of conditions

Pelton wheel turbine
Prony brake assembly
Pipe flow and head meters in approach pipe

• Open the surge tank valve and run the water supply pump to purge air from the laboratory pipe system. You may need to open flow lines at other parts of the lab to get the air out of the system
• The turbine should be run for half an hour before testing to warm up the bearings.
  • You can use this time to establish correction values for various parameters, measure necessary physical dimensions; e.g., zero correction on spring for weight of prony brake arm, radius arm of brake.
• The head should be maintained as nearly constant as possible.
  • Note that it is total head, not just pressure head, that you want to maintain constant during and between runs.
  • Since pumping surges are greater at some of the low flows used by the Pelton wheel, you may want to open a larger flow through another section of the lab.
• Set the needle valve at a partly open position.
  • You should run about half a dozen different openings at each flow, so you may want to identify them by the number of turns of the valve handle from closed position.
• Use the prony brake to set a shaft speed.
  • Tightening down slows the shaft and increases the torque.
  • Run several speeds from near stall to near runaway speed (bucket speed approaching water jet speed).
  • Adjust weights and spring to bring the prony brake arm back to a poised or free position.
• When the shaft speed is stable, take a set of readings of all variables:
  • Flow rate
  • Pressure head
  • Weights on brake
  • Force on spring
  • RPM (Note the lowest rpm on the shaft rotameter is 250 rpm, not 200.)
• Repeat this process for 5-6 shaft speeds (rpm) over the range of the Prony brake unit.
  
  
• Change the flow rate and repeat the procedure over full range of flows

PELTON WHEEL TURBINE – RESULTS

Format: Memo Report.

Present the key results and describe any major deviations from the printed procedures and why you did them.
You do not need to turn in the lab procedure sheet with your report, but it is ok to add it as an attachment. You may use a computer sketch of the apparatus in the body of the report, but the attachment must be hand drawn.

RESULTS:

Plot the curve of efficiency (e) vs. angular speed (N in RPM) for each Q. Comment on the best efficiency point (BEP) for each Q in terms of the speed factor Φ. Are they consistent with the theoretical value Φ=0.5?
[Speed factor is velocity of rotating edge divided by water velocity, or (π N D/60) / (2gH) ^0.5]

Plot the iso-efficiency curves, Q vs. N, in terms of specified efficiencies. Locate the BEP and its corresponding Q and N. Also, calculate the parameter specific speed (n_s).

Plot the torque vs. angular speed N for each experimental Q. What is the relationship between torque and angular speed N for any concerned Q.

Attach your sketch of the experimental set-up and copies of your input data and calculated results.
Write out the key equations used in calculating the results, with one sample calculation for each equation.

REFERENCE:

Roberson, J.A.. & Crow, C.T., 1997, ENGINEERING FLUID MECHANICS, 6^th ed., John Wiley and Sons, Ch 15
Daugherty, R. L., and J. B. Franzini, 1977, FLUID MECHANICS WITH ENGINEERING APPLICATIONS. 7th Ed., McGraw Hill Book Co. Chap. 14 and 15.

Sacramento State University         Dept. of Civil Engineering
CE 135 Hydraulics Lab                       Instructor      MEH

PELTON WHEEL TURBINE -- INPUT (OBSERVED) DATA

Lab. Team Name:                                                                              Date of Experiment:

CE 135 Hydraulics Lab        Instructor      MEH