The Pelton Wheel
1 Objectives
The Pelton Wheel is a machine used to convert energy to shaft power, which could be used to drive an electric generator. The Pelton Wheel consists of a number of a number of blades, sometimes called buckets, that are struck by a fluid jet to create rotational motion. The purpose of this experimental programme is to obtain power output data in terms of rotational speed for a fixed inlet condition. This relationship should be compared on a, graph with the experimental data obtained showing where the maximum efficiency should occur.
2 General Description
This equipment demonstrates the Pelton Turbine (wheel) characteristics i.e. torque, power and efficiency at different speed for various heads and flow rates of water.
The turbine nozzle directs water jet to the runner buckets. Nozzle pressure is indicated by a pressure gauge. Torque by a prong brake with two spring balances. Speed is indicated on a portable tachometer which is separately supplied. Flow rate is measured by the Hydraulics bench measuring tank. The apparatus has a hose with a quick male coupling for connection to the Hydraulics bench.
2.1 Technical Data
• 160 mm diameter stainless steel runner.
• Maximum speed approximately 1500 rpm.
• Maximum power over 30 W for 0.37 kW pump
• 0-3 kg/ cm2 pressure gauge.
Turbine Input Power, Pinput
Turbine input power can be calculated by time from the flow rate, Q, through the nozzle to the pressure at the nozzle, then:
Pinput P X Q (7)
where,
Pinput : Turbine input power.
Q: Flow rate.
p: Nozzle pressure.
Turbine Output Power, Poutput
Turbine output power or Brake power is normally measured by a mechanical dy¬namometer and is equal to:
Poutput = Tω = (F x R) x 2Πn/60
where,
Poutput,actual: Turbine actual output power or brake power, W.
T: Torque on dynamometer, N.m.
ω: Angular velocity of dynamometer, .5-1.
F: Net force on the dynamometer, N.
n: Speed of dynamometer, rpm.
R: Radius of dynamometer, m (To be measured).
3 Turbine Efficiency, η
Turbine efficiency is the ratio between power output to power input of the turbine, then:
η = Poutput/ Pinput
4 Test Procedure
The flow rate is measured by a Hydraulics bench measuring tank as well as a rotame¬ter, the pressure by a pressure gauge, the turbine speed by a portable tachometer and the forces on the Prony brake are measured by spring balances. Figure 5 shows a schematic of these measuring systems.
The students are expected to prepare and write their own test procedures after the explanation of your lecturer.
5 Report Requirements:
1. Measure the explained parameters for a given nozzle pressure and then list them in the tables provided.
2. Measure the explained parameters for the nozzle pressures of 1, 1.1, 1.2 and 1.3 bar.
3. In your report's background section describe different types of turbines with at least one example for each category.
4. Plot the following parameters and discuss their variations:
Figure 5: Schematic of the Pelton Wheel Apparatus.
• Torque vs. speed at given flow rates and nozzle pressures.
• Flow rate vs. nozzle pressure.
• Turbine output power vs. speed at given flow rates and nozzle pressures.
• Turbine efficiency vs. speed at given flow rates and nozzle pressure.
5. The analysis should also contain the following parts:
• A derivation of the Pelton Wheel relationship:
η = 2ωR/V(1 - ωR/V)(1-cosθ)
• Why is this lab exercise useful? Where can the results be used in engi-neering design/industry?
• Prom your experimental setup what will be the maximum output power?
• Give some recommendations to improve maximum obtainable power from the Wheel?
• What can you conclude from this lab exercise? How do your findings relate to engineering design?
6. Provide your detailed sample calculation in an appendix section.
Attachment:- LAB.pdf