Difference between an impulse and a reaction turbine

Impulse turbine

Reaction turbine

1. The entire available energy of water is first converted into kinetic energy.
2. The water flows through the nozzles and impings on the buckets which are fixed to the outer periphery of the wheel.
3. The water strikes on the buckets with kinetic energy.
4. The pressure of the flowing water does not change. It is equal to the atmospheric pressure.
5. It is not essential that the wheel should run full. There should be free access of air between vanes and the wheel.
6. The water must be admitted over a part of circumference or the over the whole circumference of the wheel.
7. It is possible to regulate the flow without loss.
8. The work is done by the change in kinetic energy of the jet.

1. In reaction turbine, the available energy of water is not converted into one form to another.
2. The water is guide by the guided blades to flow over the moving vanes.
3. The water move smoothly over the moving vanes with pressure energy.
4. The pressure of the flowing water is reduced after moving smoothly over the vanes.
5. It is necessary that wheel should always run full, and kept full of water.
6. The water must be admitted over the whole circumference of the wheel.
7. It is not possible to regulate the flow without loss.
8. The work is done partly by the change in velocity head. But almost all work is done by the change in pressure head.