Impulse and reaction turbine are compared below presented in picture and tabular form.
|Schematic diagram summarising the differences between impulse turbine and reaction turbine,
where the rotor is the rotating part and the stator is the stationary part of the machine.
Image source: Emoscopes (Wikimedia Commons)
Differences between Impulse and Reaction Turbines:
|1||In impulse turbine all hydraulic energy is converted into kinetic energy by a nozzle and it is is the jet so produced which strikes the runner blades.||In reaction turbine only some amount of the available energy is converted into kinetic energy before the fluid enters the runner.|
|2||The velocity of jet which changes, the pressure throughout remaining atmosphere.||Both pressure and velocity changes as fluid passes through a runner. Pressure at inlet is much higher than at outlet.|
|3||Water-tight casing is not necessary. Casing has no hydraulic function to perform. It only serves to prevent splashing and guide water to the tail race.||The runner must be enclosed within a watertight casing.|
|4||Water is admitted only in the form of jets. There may be one or more jets striking equal number of buckets simultaneously.||Water is admitted over the entire circumference of the runner.|
|5||The turbine doesn’t run full and air has a free access to the bucket.||Water completely fills at the passages between the blades and while flowing between inlet and outlet sections does work on the blades.|
|6||The turbine is always installed above the tail race and there is no draft tube used.||Reaction turbine are generally connected to the tail race through a draft tube which is a gradually expanding passage. It may be installed below or above the tail race.|
|7||Flow regulation is done by means of a needle valve fitted into the nozzle.||The flow regulation in reaction turbine is carried out by means of a guide-vane assembly. Other component parts are scroll casing, stay ring runner and the draft tub.|
|8||Example of impulse turbine is Pelton wheel.||Examples of reaction turbine are Francis turbine, Kaplan and Propeller Turbine, Deriaz Turbine, Tubuler Turbine, etc.|
|9||Impulse turbine have more hydraulic efficiency.||Reaction turbine have relatively less efficiency.|
|10||Impulse turbine operates at high water heads.||Reaction turbine operate at low and medium heads.|
|11||Water flow is tangential direction to the turbine wheel.||Water flows in radial and axial direction to turbine wheel.|
|12||Needs low discharge of water.||Needs medium and high discharge of water.|
|13||Degree of reaction is zero.||Degree of reaction is more than zero and less than or equal to one.|
|14||Impulse turbine involves less maintenance work.||Reaction turbine involves more maintenance work.|
thanks for this comparison this was useful
This is extremely useful tabulation & clear illustration.
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Very nice explaination
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Now I have understood the difference between the two classifications. Thanks a lot.
Nice one difference between the two turbines
Thanks for a simple elaboration of the two turbines
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