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Pelton wheel

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image:peltonturbine-1.jpg thumb|240px|right|Pelton wheel from [[Walchensee, Germany Hydroelectricity hydro power station. ]] A '''Pelton wheel''', also called a '''Pelton turbine''', is one of the most efficient types of water turbines. It is an Impulse machine, meaning that is uses Newton%27s_laws#Newton.27s_Second_Law Newton's second law to extract energy from a jet of fluid.

Function
The pelton wheel turbine is a tangential flow impulse turbine, water flows along the tangent to the path of the runner. Nozzles direct forceful streams of water against a series of spoon-shaped buckets mounted around the edge of a wheel. Each bucket reverses the flow of water, leaving it with diminished energy. The resulting impulse spins the turbine. The buckets are mounted in pairs, to keep the forces on the wheel balanced, as well as to ensure smooth, efficient momentum transfer of the fluid jet to the wheel. The Pelton wheel is most efficient in high head (hydraulic) head applications. Since water is not a compressible fluid, almost all of the available energy is extracted in the first stage of the turbine. Therefore, Pelton wheels have only one wheel, unlike turbines that operate with compressible fluids.

History
Lester Allan Pelton, carpenter and millwright, invented the Pelton wheel in 1879 while working in California. He obtained his first patent in 1880. The prototype Pelton wheel is on display in Camptonville, California Camptonville and was designated an List_of_Historic_Civil_Engineering_Landmarks Historic Civil Engineering Landmark in 1973[http://www.asce.org/history/pwr_pelton.html]. One story has Pelton inventing his wheel by noticing how water splashed out of the nostrils of a cow as it drank from a stream. In another story he is inspired by a water wheel whose axle came loose while he was working on it. The water jet hit the edge of the water wheel bucket and reversed direction (instead of filling the bucket). Pelton observed an increase in speed of the misaligned wheel.

Applications
Image:S vs pelton schnitt 1 zoom.png thumb|240px|right|Plan view of a pelton turbine installation (courtesy Voith Siemens Hydro Power Generation). Peltons are the turbine of choice for high head, low flow sites. However, Pelton wheels are made in all sizes. There are multi-ton Pelton wheels mounted on vertical oil pad bearing bearings in the generator houses of hydroelectric plants. The largest units can be up to 200 watt megawatts. The smallest Pelton wheels, only a few inch inches across, are used with household plumbing fixtures to tap power from mountain streams with a few gallons per minute of flow, but these small units must have thirty meters or more of head. Depending on water flow and design, Pelton wheels can operate with heads as small as 15 meters and as high as 1,800 meters. In general, as the height of fall increases, less volume of water can generate the same Power (physics) power. Energy is force times distance, and the higher pressure can apply the same force with less mass flow. Every installation therefore has its own most-efficient pressure, speed and volume. Usually small installations use standardized buckets, and adapt the turbine to one of a family of generators and wheel sizes by using custom plumbing. Small turbines can be adjusted somewhat by varying the number of nozzles and buckets per wheel, and choosing different diameters of wheel. Large installations custom design the turbine's torque and volume to turn a standard generator. Many small installations also can double as a developed source of pressurized household wash water, or animal feed water. In areas where household water is cheap enough, a Pelton wheel can generate power from household water. A typical item in most Pelton wheel installations is the governor (device) governor. It modulates the flow of water based on the speed of the wheel and this speed will determine the frequency of the alternating frequency current produced by an attached AC generator.

See also
*Water turbine *Turbine *Hydropower

External links

- NASA site
- Pelton wheel photos
- MicroHydroPower Pelton Information Category:Turbines Category:Historic civil engineering landmarks Category:Renewable energy Category:Energy conversion de:Pelton-Turbine es:Turbina Pelton fr:Turbine Pelton it:Turbina Pelton ja:ペルトン水車 no:Peltonturbin nn:Peltonturbin sl:Peltonova turbina

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