impulse and reactionturbine

8/13/2019 Impulse and Reactionturbine

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09 ME 93 Yasir hashmi

QUEST Nawabshah


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Turbines A turbine is a rotary engine that exerts energy from a

fluid flow and converts it into useful work.


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There are two basic types of turbines according tothe mode of steam.

1. Impulse turbine

2. Reaction turbine


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Impulse turbine

Working principle It runs by impulse of steam.

Nozzle directs the steam on the curved blades, which

causes them to rotate. The blades are in the shape of buckets.


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The energy to rotate an impulse turbine is derived

from the kinetic energy of the steam flowing throughthe nozzle.

The potential energy is converted into kinetic energywhen it passes through the nozzle.

The velocity of steam is reduced when it passes overthe blades.


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Reaction turbine

Working principle It has no nozzle. Two rows of moveable blades are separated by one row of

fixed blades.

Fixed blades are attached to the casing & act as nozzles. Blades are like the wings of a plane.


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Velocity of steam is increased when it passes throughthe fixed blades.

The enthalpy drop in moving blades is called degree ofreaction.

A common arrangement can have 50% of enthalpydrop in moving blades, it is said to have 50% reaction.

If all enthalpy drops in moving blades then it is said tobe 100% reaction.


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Difference between impulse and

reaction turbine

S.NO Impulse turbine Reaction turbine

1.The steam flows through thenozzle and impinges on themoving blades.

The steam first flows through theguide mechanism and then throughthe moving blades.

2.The steam impinges on thebuckets with kinetic energy.

The steam glides over the movingvanes with pressure and kineticenergy.

3.

The steam may or may not be

admitted over the wholecircumference.

The steam pressure is reduced

during its f low through the movingblades.

4. The blades are symmetrical The blades are not symmetrical


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Efficiency To maximize the efficiency of steam turbine the steam

is expanded, generating work in a number of stages.

Multiple stages turbines are highly efficient.

Most steam turbines use a mixture of both impulseand reaction design.

Higher pressure sections are impulse type and lower

pressure sections are reaction type.


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Advantages of steam turbine It can develop higher speeds.

The steam consumption is less.

All the parts are enclosed in a casing so it is safe. It requires less space and lighter foundations.

There is very less friction in the turbine due to fewsliding parts.


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Uses Turbines are used in force draft blowers, pumps and

main propulsion turbines.

Used in the jet engines and air crafts.

They are also used in power plants , ships andsubmarines.


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Pressure velocity graph of impulse and reactionturbines.


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Thanks

impulse and reactionturbine

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