Turbine: Pelton Wheel the Common form of Impulse Turbine



Pelton wheel is common example of Impulse Turbine.Pelton Wheel is used for high water head and low discharge.Parts are nozzle,casing,Runner and Buckets
Turbines are the modern machines used to generate electricity in power plant. In Hydro-Electric Power Plant Impulse Turbine and Reaction Turbine are used based on the requirement. The common example of Impulse Turbine is Pelton Wheel. This turbine is developed by Pelton L.A. who was California based engineer. Pelton Wheel Turbine is used for high water head and low discharge.

 

The main parts of Pelton Wheel

 

01) Nozzle

It is the circular guide mechanism, which guides the water to flow at designed direction and regulate the flow rate. A conical needle or spear operates inside the nozzle in an axial direction. This spear controls the quantity of water flowing through the nozzle. The area of jet is reduced by pushing the spear forward inside the nozzle, this results in reduction of water quantity flowing through the jet. Similarly, if the spear is pushed back, the greater quantity of water is flow through the jet. Spear is controlled by automatic governing mechanism or by hand depending upon the need. Some additional nozzles, known as Bypass Nozzles are provided to avoid the bursting of pipe in case of sudden closing of water supply. Bypass nozzle don’t allow water to strike the buckets. In some Pelton Wheel defectors are provided in nozzle, which is used to defect the water jet and preventing it from striking the buckets.
 
02) Runner and Buckets
The runner of a Peton Wheel consists of a circular disc fixed to a horizontal shaft. On the periphery of the runner number of buckets in hemispherical or bowl shape is fixed uniformly. The surface of buckets is made very smooth to avoid friction losses. The material of bucket for low water head is Cast Iron, for high head, they are made from bronze, Stainless Steel or other alloy. Special Alloys are used to manufacture buckets when water is chemically impure. The buckets are generally bolted on runner disc so when few buckets are worn and needs replacement, that can be done.
 
03) Casing

The casing is, generally, made of cast or fabricated parts, to safeguard the runner and bucket assembly against accident and also to prevent the splashing of water and lead the water to the tail race. Casing of Pelton Wheel does not perform any hydraulic function.

 

04) Braking Jet

To reduce the speed of the runner, braking jet is work as brake. These are very small nozzles in order to bring runner to rest in short time period. Braking jet works on back side of buckets. This jet, broughtturbine to rest for necessary action to do by engineering dept.
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Hi,This is Prasanna talking with you.I am mechanical engineer by eduction and profession.Here I shared all my engineering tutorials with you.If you like these tutorials,please spread it with world. Prasanna Sutrave