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Pelton Turbine

Pelton Turbine

The Pelton turbine is a type of turbine used in the hydropower industry within the field of renewable energy.

A Pelton turbine is a hydraulic turbine of the impulse type used in hydroelectric power plants with high vertical height. It was Invent to by Lester Allan Pelton in the 1870s and Amend significantly by other inventors beyond late 1800. The Pelton turbine is a further development of traditional water wheel. The Pelton turbine transforms the hydropower into the impulse of one or more jets of water at a very high velocity to kinetic energy (rotation). There were many variants of the drive turbines before the invention of the Pelton turbine , but they had a lower efficiency.

The Pelton turbine is usually installed in a  hydropower station and connected to a pressure pipe from a high-altitude dam. In the turbine, the water is fed to one or more nozzles, and there is a violent acceleration in the water flow. The water has a very high velocity when it leaves the nozzle and rises to the impeller of the turbine. The water jet hits several bowl-shaped paddles, which are characteristic of the turbine type.On the shaft of the turbine there is a generator that produces electrical energy.

In the above types of turbines, water still had a high speed when aba abandon the wheel, so much of the kinetic energy of water not used completely. Pelton designed the blades so that the water jet rotates almost 180 ° after leaving the blades. When the peripheral speed of the impeller has approximately half the speed of the water flow, the greatest effect is achieved. The water comes out of the turbine wheel at very low speed. A Pelton turbine has an efficiency of 92% in the use of hydropower .

Structure of the Pelton turbine

The main components of the Pelton turbine consist of an impeller, a shaft, a feed pipe, one or more nozzles and turbine housings. Then, in principle, the same parts as in Pelton's time. The supply tube in a modern Pelton turbine is a main ring with bends made to the nozzles. Often there are more nozzles from which the water is distributed from the supply pipe, and when the water accelerates sharply before it touches the impeller blades.

The impeller rotates outdoor completely and placed in a housing or cover, often called the turbine housing, which catch water splashes l as the tunnel will drain  hydropower plant. The pressure in the water in the ring line just before the nozzles is determined by the height of fall. The housing of the Pelton turbine is filled with air at atmospheric pressure (1 bar). Through the nozzles, the water accelerates while the pressure in the water drops to atmospheric pressure. Since the pressure in the water does not change before and after contact with the impeller, a skin turbine can be called a liquid pressure turbine.

The scroll wheel is mounted on a vertical or horizontal axis that is equipped with one or more bearings. Normally, horizontal axes are used for hydraulic  turbines with one or two spokes, while one selects the vertical axis if there are more beams. The nozzle or nozzles on the Pelton turbine are mounted so that the water jet hits the outermost blades on the impeller at right angles.

The blades are mounted firmly so that the water jet touches each blade for a moment. Because the water has a certain velocity after it has left the containers, it quickly disappears from the impeller, so the containers are empty of water when they reach the next stream of water. The collision between the water drops and the back of the bowls represents a certain problem. The design of the Pelton turbine is made to use the water quickly.

The plates in the impeller are double in the way that in the middle of each blade there is a quasi-egg that cuts the water jet. Each one of the two halves of the container diverts half of the water jet, and when it has to follow the outline of the containers, the water makes a "U-turn". Each half of the split water jet passes virtually a 180 ° curve before leaving the outer edge of the container. This balances the lateral load forces on the wheel and shaft. The fact that the water makes a "U-turn" is a prerequisite for the best possible use of the water jet impulse. So that the water jet is not cut by the container directly in front of the one that causes the water jet to straighten, a notch (recess) is made in the outermost part of each container.

In modern high-pressure Pelton turbines , the impeller is made from a single piece of forged steel. For low pressure hydropower plants , it is common for the bowls to be screwed to the wheel, while this was the only form of construction.

The jet of water exerts a force on each of the plates, and the product of this force and the radius from the center of the impeller to where the beam hits the pair of forces of the turbine (force by the arm). When the impeller rotates, the work corresponding to the definition is performed, which establishes that the work is equal to the moment multiplied by the speed of rotation (angular velocity).

The potential energy of the water in the intake tank of the hydropower plant is transformed into kinetic energy (rotation) in the turbine. A small part of the original kinetic energy in the water flow remains in the water after the wheel has turned to the next bowl. This means that not all the energy in the water is used, but as mentioned above, this is necessary for the water to quickly exit the impeller. This prevents the collision between the water and the back of the bowls, which in turn will reduce the speed of the wheel.

The effect that a Pelton turbine can develop is as with all other hydraulic  turbines determined solely by efficiency, drop height and water flow.

Application of the Pelton turbine

The Pelton turbine is the preferred type of turbine for the use of waterfalls with high drop height and small amounts of water. The highest drop height for a power plant in the world is the Bieudron power plant in Switzerland, with a drop height of 1883 m. This power plant has the three most distant turbines, the largest in the world with a performance of 423 megawatts ( MW ) each.

Pelton turbines are also used in small power plants, hydropower plants and hydroelectric power plants mini. Installations where the height of fall is a few tens of meters and the extinction of a few liters per second is not uncommon.

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Last review: December 5, 2018