Reaction Turbines

What is a reaction turbine? How to calculate hydraulic and overall efficiency of reaction turbine? What is difference between a Kaplan turbine and Francis turbine?

The following important points may be noted for reaction turbines :

(a) In a reaction turbine, the water enters the wheel under pressure and flows over the vanes.

(b) The hydraulic efficiency of a reaction turbine is the ratio of the workdone on the wheel to the energy (or head of water) actually supplied to the turbine.

(c) The overall efficiency of a reaction turbine is the ratio of the power produced by the turbine to the energy actually supplied by the turbine.

(d) A Kaplan turbine is an axial flow reaction turbine. The number of blades are generally 4 to 8 in a Kaplan turbine runner.

(e) A Francis turbine is an outward flow reaction turbine. The number of blades are generally 16 to 24 in a Francis turbine runner.