Diagram of Pelton Wheel:-
Explanation (Working): The water stored at high head is made to flow through the penstock and reaches the nozzle of the Pelton turbine. The nozzle increases the K.E. of the water and directs the water in the form of jet. The jet of water from the nozzle strikes the buckets (vanes) of the runner. This made the runner to rotate at very high speed. The quantity of water striking the vanes or buckets is controlled by the needle valve present inside the nozzle. The generator is attached to the shaft of the runner which converts the mechanical energy ( i.e. rotational energy) of the runner into electrical energy.
Diagram of Pelton Wheel:-
Construction of Pelton Wheel Turbine:
1. Runner with Bucket: The runner of a pelton turbine consists of a number of double cupped buckets surrounded to the periphery of the wheel. Material for bucket is cast iron for low head plant and cast steel, stainless steel and bronze for medium and high heads. The buckets are either cast integral with the wheel or bolted to the rim. Bolted arrangement is preferred as the damaged bucket can be easily replaced.
2. Nozzle with guide mechanism: The function of the nozzle of a pelton wheel is to convert the available pressure energy into high velocity energy in the form of jet. The quantity of water required is proportional to the load on the turbine. Therefore, to control the flow through the nozzle, some most of a regulating or a governing mechanism is necessary. This is generally done by using a spear inside the nozzle. A brake nozzle is used in case of large turbine. When the wheel is to be stopped, besides cutting off the supply of water through the main nozzle.
3. Casing : Casing of a pelton turbine is not to perform any hydraulic function. However, a casing is necessary to avoid accidents, splashing race and to support the housing for the bearing and the nozzle.