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In this experiment, the performance characteristics of a Pelton wheel hydraulic turbine will be
determined.
The Pelton wheel hydraulic turbine is driven by a jet of water from a nozzle that strikes
the buckets on the wheel.
The water jet causes the wheel to rotate, producing torque and power. The water itself
is supplied by a pump inside a hydraulics bench.
A brake system is used to measure the torque on the shaft. This system includes two spring
balances connected by a cord that wraps around the shaft.
The flowrate of the water jet is controlled by a spear valve. After the water leaves the
turbine casing it empties into the hydraulic bench where its volumetric flowrate can be
measured.
A pressure gauge is located near the spear valve and can be used to determine the head
available to the fluid.
Before starting the experiment, make sure all valves are closed.
Then ensure there is no tension in the cord connecting the spring balances.
Finally, ensure that water can flow into the drain freely.
Close both the spear valve on the Pelton wheel turbine and the valve on the hydraulics bench.
There should be no tension in the cord connecting the spring balances before starting the experiment.
Adjust the screws at the top of the spring balances until the cord hangs loosely from
the hooks. Note any offsets in the force readings.
Remove the drain column from the drain and set it aside.
The experiment first will be conducted at maximum flowrate with both valves fully opened.
After the pressure reading is recorded, the turbine speed will be varied and the corresponding
force readings recorded. Finally, the volumetric flowrate will be measured. Then the same procedure
will be used at a lower flowrate.
Turn on the pump in the hydraulics bench. Then fully open the bench's valve.
Slowly open the spear valve until it is fully open. The resulting water jet will drive the
Pelton wheel.
Record the pressure reading from the pressure gauge.
Increase the load on the shaft by increasing the tension on the spring balances. Adjust
the screw above both spring balances until the rotational speed slows to approximately
750 rpm, as indicated by the handheld digital tachometer.
The tachometer should be aimed at the path of the white square just off-center of the
hub. The tachometer reading will vary slightly in time, so estimate the average rotational
speed over the course of a few seconds.
Record both forces indicated on the spring balances.
Reduce the rotational speed in increments of 100 rpm all the way down to 150 rpm by
adjusting the screws on the spring balances.
Record the forces on the spring balances at each speed.
The volumetric flowrate is determined by plugging up the drain at the bottom of the bench with
the drain column and observing the waterline on the side of the bench.
Make sure the rubber gasket is placed between the drain column and the drain.
Start the timer when the waterline reaches 0 liters and stop it when it reaches 25.
The volumetric flowrate is 25 liters divided by the measured time.
Once you have finished recording the flowrate, remove the drain column and set it aside.
Reduce the flowrate by closing the spear valve completely and then re-opening it only two
turns.
Release the tension in the cord connecting the spring balances and repeat the procedure
at the reduced flowrate.
Examine turbine performance at rotational speeds from approximately 1050 rpm down to
150 rpm, in increments of 100.
When finished with this lab, close both valves and then turn off the pump.
Then release both the pressure in the feed line and tension on the spring balances.
Finally pour out the water from the drain column.
Close the spear valve, then close the flow control valve on the hydraulics bench and
turn off the pump.
Release the pressure in the feed line by briefly opening the spear valve.
Adjust the screws at the top of the spring balances to release the tension.
Finally, carefully pour the water out of the drain column and place it back into the drain.