A turbine is a rotary engine that extracts energy from a fluid flow and converts it into useful work.It converts the energy of rushing water, steam or wind into mechanical energy to drive a generator.Then generator produce electricity with mechanical energy given by turbine.
Turbine type according to available head
Propeller up to 15 metres Kaplan up to 30 metres Francis 10 to 300 metres Pelton 300 metres and over
Since they can reach very high rotation speeds, propeller turbines are effective for low heads. Consequently, this type of turbine is suitable for run-of-river power stations.
The Pelton turbine is an impulse turbine.It requires tangential water flow on one side of the wheel and must therefore operate when only partly submerged. It is best suited to applications with a high head but a low volume flow rate such as fast flowing shallow water courses though it is used in a wide range of situations with heads from as low as 15 metres up to almost 2000 metres. High pressure heads give rise to very fast water jets impinging in the blades resulting in very high rotational speeds of the turbine.Pelton wheels are ideal for low power installations with outputs of 10kW or less but they have also been used in installations with power outputs of up to 200 MW. Efficiencies up to 95% are possible.Named after its American inventor, Lester Pelton (1829-1908), this turbine uses spoon-shaped buckets to harness the energy of falling water.
Francis turbine is mainly used in hydro electric power plants.It was named after James Bicheno Francis (1815-1892), the American engineer who invented the apparatus in 1849.The Francis turbine is a reaction turbine designed to operate fully submerged. Water flow enters in a radial direction towards the axis and exits in the direction of the axis. Its is suitable for lower heads of water of 500 metres or less and is the most commonly used high power turbines. Large scale turbines used in dams are capable of delivering over 500 MW of power from a head of water of around 100 metres with efficiencies of up to 95%.
The propeller turbine, is an example of a reaction turbine. Designed to work fully submerged, it is similar in form to a ship’s propeller and is the most suitable design for low head water sources with a high flow rate such as those in slow running rivers. Designs are optimised for a particular flow rate and efficiencies drop of rapidly if the flow rate falls below the design rating. The Kaplan version has variable pitch vanes to enable it to work efficiently over a range of flow rates.Austrian engineer Viktor Kaplan (1876-1934) invented this turbine. It’s similar to the propeller turbine, except that its blades are adjustable; their position can be set according to the available flow.