INTRODUCTION: The Pelton wheel turbine is a tangential flow impulse turbine. The water strikes the bucket along the tangent of the runner. The energy available at the turbine is only kinetic energy. This turbine is used for high head and is named after the American engineer Lester Pelton.
CONSTRUCTION DETAILS OF PELTON TURBINE: Components of the Pelton turbine:-
- Nozzle: – the amount of water striking the vanes (buckets) of the runner is controlled by providing a spear (flow regulating arrangement) in the nozzle.
- Spear: – the spear is a conical needle which is operated either by a hand wheel or automatically in an axial direction depending upon the size of the unit.
- Runner with bucket: – runner of Pelton wheel consists of a circular disc on the periphery of which a number of buckets evenly spaced are fixed.
- Casing: – casing is to prevent the splashing of the water and to discharge water to tail race. It is made up of cast iron or steel plate.
- Breaking jet: – when the nozzle is completely closed by moving the spear in the forward direction the amount of water striking the runner reduce to zero.
But the runner due to inertia goes on revolving for a long time. To stop the runner in a short time, a small nozzle is providing which directs the jet of water on the back of vanes. This jet of water is called breaking jet.
- Governing mechanism: – speed of turbine runner is required to be maintained constant so that electric generator coupled directly to turbine.
WORKING OF PELTON TURBINE
The amount of water striking the vanes (buckets) of the runner is controlled by providing a spear (flow regulating arrangement) in the nozzle.
Then the efficient nozzle that converts the hydraulic energy into a high speed jet. The turbine rotor is called runner.
The impact jet of water is striking on the runner and runner revolves at constant with the help of governing mechanism.
The runner shaft is connected with the generator; thus the electricity is produce with the help of generator.
EFFICIENCIES OF PELTON TURBINE
· Mechanical efficiencies: – It is ratio of the shaft power to the water power.
· Hydraulic efficiencies: – It is ratio of the power developed at the turbine runner to the power supplied by the water jet at entrance to the turbine.
· Volumetric efficiencies: – It is ratio of the theoretical to the actual discharge.
· Overall efficiencies: – It is ratio of the shaft power to the water power.