Pelton wheel turbine is from the impulse turbine categories of hydraulic turbine. It is name after its inventor Allan Pelton. There are many other types of impulse turbine but Pelton turbine is the most efficient from all of them.
Parts of Pelton Turbine
Pen stockPen stock is a solid pipe which take water from the dam( structure which store water on its one side) and take it to the turbine at very high speed.
SpearA spear is provided with in the pen stock and its main function is to increase and decrease the speed of water entering into the turbine. If more water is needed spear move back and allow more to enter into the turbine and if less water is needed spear moves forward to spot excess water from entering in to the turbine.
NozzleNozzle is provided at end of pen stock and its main function is to increase the velocity of the water and to direct it to the buckets of the turbine.
BucketsEach pelton turbine has a specific number of buckets attached to its runner. Buckets take the impact of water and start to rotate along the runner
RunnerRunner is a heavy circular disc on which buckets are attached. Runner is further attached to the shaft.
Brake nozzleWhen turbine is need to be stopped then water is thrown at the back of the buckets from another nozzle called brake nozzle
CasingThe whole setup of the turbine is enclosed in a structure called the casing of the turbine
Working of the pelton turbineDam store water at its one side when water level is increased at a specific height then the gates of the dam is open and water start to flow through the pen stock. Nozzle at the end of the pen stock convert this high speed water into a water jet which on striking the bucket convert its kinetic energy into the rotation energy of the buckets and the runner. Runner is attached to the shaft which is further attached to a generator. Rotating runner rotates the shaft which rotates the generator.
Hydraulic efficiencyIt is the ratio of the power developed by runner to the power supplied at in let of turbine
Mechanical efficiencyIt is the ratio of the power available at turbine shaft to the power available at turbine runner
Volumetric efficiencyIt is the ratio of volume of water actually striking the runner to the total water supplied by the jet to the turbine
Overall efficiencyIt is the ratio of the power available at the turbine shaft to the power available from the jet
Advantages of Pelton turbine
- Most efficient of all turbines
- High overall efficiency
- Easy assembly
- Operate at low discharge
- Flat efficiency curve
- Can be operation in silted water
Disadvantages of Pelton turbine
- Decrease in efficiency with time
- Components have large size
- Variation in the operating head is very difficult to control
- The operating head cannot be utilized even when the variation in the tail water level is relatively large when compared to total head