Pelton Turbine

A Pelton turbine or Pelton wheel is a type of turbine used frequently in hydroelectric plants. These turbines are generally used for sites with heads greater than 300 meters. This type of turbine was created during the gold rush in 1880 by Lester Pelton.

When used for generating electricity, there is usually a water reservoir located at some height above the Pelton turbine. The water then flows through the penstock to specialized nozzles that introduce pressurized water to the turbine. To prevent irregularities in pressure, the penstock is fitted with a surge tank that absorbs sudden fluctuations in water that could alter the pressure.Unlike other types of turbines which are reaction turbines, the Pelton turbine is known as an impulse turbine. This simply means that instead of moving as a result of a reaction force, water creates some impulse on the turbine to get it to move.

1. Nozzle and Flow Regulating Arrangement (Spear)

§ Nozzle is used to increase the kinetic energy of the water that is going to strike the buckets or vanes attached to the runner.

§ The quantity of water that strikes the buckets is controlled by spear. The spear is installed inside the nozzle and regulates the flow of water that is going to strike on the vanes of the runner. A nozzle containing spear is shown in the figure given below.

§ The spear is a conical needle present in the nozzle. It is operated by a hand wheel or automatically in an axial direction.

§ When the spear is move backward the rate of flow of water increases and when it is pushed forward the rate of flow of water decreases.

2. Runner and Buckets

The runner with buckets is shown in the figure given below.

§ Runner is a rotating part of the turbine. It is a circular disc on the periphery of which a number of buckets evenly spaced are fixed.

§ The buckets are made by two hemispherical bowl joined together. Each buckets have a wall in between two hemispherical bowl called splitter.

§ The splitter splits the jet of water striking the buckets into two equal parts and the jet of water comes out at the outer edge of the bucket.

§ The buckets are designed in such a way that the jet of water strike the buckets, deflected through 160 degree  to 170 degree.

§ The buckets of the Pelton turbine are made up of cast iron, cast steel bronze or stainless steel.

3. Casing:

The outer covering of the this turbine is called casing. The Pelton turbine with the casing is shown in the figure given below.

4. Breaking jet

§ When the jet of water is completely closed by pushing the spear in forward direction than the amount of water striking the runner becomes zero. But still the runner keeps moving due to the inertia of the runner.

§ In order to stop the runner in the shortest possible time a small nozzle is provided which directs the jet of water at the back of the vanes. This jet of water used to stop the runner of the turbine is called breaking jet.