Selection of turbine with respect to head versus specific speed

Electrical Department Bahria university Islamabad

Group Member• Junaid Maqsood • Talha Ali

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Contents

Turbine & its design Types of Turbine Types of turbine on Basis of Head Types of turbine Based on specific speed Selection of turbine Turbine Application Chart Conclusion

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Turbine What is turbine ?

•“turbo” or “turbines” is Latin in origin and implies that which spins or whirls around •Turbine is a device that extracts energy from a fluid

•Energy is transferred to or from a continuously flowing fluid by the dynamic action of moving blades or rotors

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Turbine Design

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Types of Turbines

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Impulse Turbine

• IMPULSE TURBINE

The impulse turbine generally usesthe velocity of the water to move the runner and discharges to atmospheric pressure. The water stream hits each bucket on the runner. There is no suctionon the down side of the turbine, and the water flows out the bottom of the turbine housing after hitting the runner. An impulse turbine is generally Suitable for high head, low flow applications.

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REACTION TURBINE

• REACTION TURBINEA reaction turbine develops power from the combined action of pressure and moving water. The runner is placed directly in the water stream flowing over the blades rather than striking each individually. Reaction turbines are generally used for sites with lower head and higher flows than compared with the impulse turbines

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Selection of turbine• The turbine is always selected to match the specific conditions under

which it has to operate and attain the maximum possible efficiency.

• Head Flow/Speed

• For selection of suitable turbine, the characteristics features of common turbines based on experience are given in further slides.

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Types of turbine on Basis of Head

Based on head and quantity of waterAccording to head and quantity of water available, the turbines can be classified into

a) High head turbines

b) Medium head turbines

c) Low head turbines

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Based on head and quantity of water

a) High head turbines

– High head turbines are the turbines which work under heads more than 250m.

– The quantity of water needed in case of high head turbines is usually small.

– The Pelton turbines are the usual choice for high heads.

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Based on head and quantity of water

b) Medium head turbines

– The turbines that work under a head of 45m to 250m are called medium head turbines. – It requires medium flow of water. Francis turbines are used for medium heads.

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Based on head and quantity of water

c) Low head turbines– Turbines which work under a head of less than 45m are called low head turbines. – Owing to low head, large quantity of water is required. – Kaplan turbines are used for low heads.

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Classification and Selection of turbine based on Head

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Choice Of turbine

Depends on available Head

•Specific Speed:

– For High Head – low specific speed so impulse turbines are required

– For Low Head – High Speed e.g Propeller

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Based on specific speed of turbines

Speed of a unit power when working under unit head.

It is denoted by the symbol Ns.

N= Speed (RPM)P = Power developedH = head under which the turbine is working

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Classification and Selection of turbine based on Head

Specific Speed m/s

Slow Medium fast

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To Vary Specific Speed

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Conclusion

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