The Pelton turbine, also known as the tangential hydraulic wheel or Pelton wheel, was invented by the American Lester Allen Pelton in the 1870s. Although several types of turbines were created before the Pelton type, this is still the most widely used currently for its effectiveness.
It is an impulse turbine or hydraulic turbine that has a simple and compact design, has the shape of a wheel, composed mainly of buckets, deflectors or divided moving blades, located around its periphery.
The blades can be positioned individually or attached to the central hub, or the entire wheel can be fitted in one complete piece. To function, it converts the energy of the fluid into motion, which is generated when a high-speed jet of water hits the moving blades, causing it to rotate and start operating.
It is generally used to produce electricity in hydroelectric plants, where the available water reservoir is located at a certain height above the turbine.
History
Hydraulic wheels were born from the first wheels that were used to draw water from rivers and were moved by the effort of man or animals.
These wheels date back to the 2nd century BC, when paddles were added to the circumference of the wheel. Hydraulic wheels began to be used when the possibility of harnessing the energy of currents to operate other machines, known today as turbomachines or hydraulic machines, was discovered.
The Pelton-type impulse turbine did not appear until 1870, when the miner Lester Allen Pelton of American origin implemented the first mechanism with wheels to draw water, similar to a mill, then he implemented steam engines.
These mechanisms began to fail in their operation. From there, Pelton came up with the idea of designing hydraulic wheels with blades or blades that receive the shock of water at high speed.
He observed that the jet struck at the edge of the blades instead of at their center and as a result the water flow was exiting in the reverse direction and the turbine speeding up, making it a more efficient method. This fact is based on the principle by which the kinetic energy produced by the jet is conserved and can be used to generate electrical energy.
Pelton is considered the father of hydropower, for his significant contribution to the development of hydropower around the world. His invention in the late 1870s, dubbed by himself the Pelton Runner, was recognized as the most efficient impulse turbine design.
Later, Lester Pelton patented his wheel and in 1888 formed the Pelton Water Wheel Company in San Francisco. "Pelton" is a trademark of that company's products, but the term is used to identify similar impulse turbines.
Later, new designs emerged, such as the Turgo turbine patented in 1919, and the Banki turbine inspired by the model of the Pelton wheel.
Operation of the Pelton turbine
There are two types of turbines: reaction turbine and impulse turbine. In a reaction turbine, the drainage takes place under the pressure of a closed chamber; for example, a simple garden sprinkler.
In the Pelton-type impulse turbine, when the buckets located on the periphery of the wheel directly receive the water at high speed, they drive the rotational movement of the turbine, converting the kinetic energy into dynamic energy.
Although both kinetic energy and pressure energy are used in the reaction turbine, and although all the energy delivered in an impulse turbine is kinetic, therefore, the operation of both turbines depends on a change in the speed of the water, so that it exerts a dynamic force on said rotating element.
Application
There is a great variety of turbines in different sizes on the market, however it is recommended to use the Pelton type turbine at heights from 300 meters to about 700 meters or more approximately.
Small turbines are used for domestic purposes. Thanks to the dynamic energy generated by the speed of the water, it can easily produce electrical energy in such a way that these turbines are mostly used for the operation of hydroelectric plants.
For example, the Bieudron hydroelectric power station in the Grande Dixence dam complex located in the Swiss Alps in the canton of Valais, Switzerland.
This plant began its production in 1998, with two world records: it has the most powerful Pelton turbine in the world and the tallest head used to produce hydroelectric energy.
The facility houses three Pelton turbines, each of them operates at a height of approximately 1869 meters and a flow rate of 25 cubic meters per second, working with an efficiency greater than 92%.
In December 2000, the gate of the Cleuson-Dixence dam, which feeds the Pelton turbines at Bieudron, ruptured at about 1,234 meters, forcing the shutdown of the power plant.
The rupture was 9 meters long by 60 centimeters wide, causing the flow through the rupture to exceed 150 cubic meters per second, that is, it had a rapid release of a large amount of water at high pressure, destroying its passage approximately 100 hectares of pastures, orchards, forests, the washing of various chalets and barns located around this area.
They conducted a large investigation into the accident, as a result they almost completely redesigned the penstock. The root cause of the rupture is still unknown.
The redesign required improvements to the pipe lining and soil improvement around the penstock to reduce the flow of water between the pipe and the rock.
The damaged section of the penstock was redirected from the previous location to find new rock that was more stable. Construction on the redesigned gate was completed in 2009.
The Bieudron facility was not operational after this accident until it was fully operational in January 2010.
References
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