Radial flow turbines are those in which the water flows in the radial direction. The water may flow radially outward to inwards or from inwards to outwards. If the water flows from outwards to inwards through runner, the turbine is known as inward radial flow turbine and if the water flows from inwards to outwards, the turbine is known as outward flow turbine.

Reaction turbine is the one in which the water at the inlet of the turbine possesses kinetic energy as well as pressure energy.

As the water flows through the runner, a part of pressure energy goes on changing into kinetic energy, Thus the water through the runner is under pressure, The runner is completely enclosed in an air tight casing, and casing and the runner is always full of water.

Main parts of Radial flow reaction turbine.

1. Casing.

2. Guide mechanism.

3. Runner.

4. Draft-tube.