Kaplan turbine is an axial flow reaction turbine best suitable for low heads (1.5 to 30 m). It can be handle large quantity of water and it runs faster with maintain high efficiency.
Kaplan turbine is more compact than Francis turbine. Water is entering in to the turbine through the guide vanes. The Stream of water then turns through the right angle and flows over runner blades.
These guide vanes and blades are adjustable. Guide vanes are turned through certain angle to regulate the water flow. Runner blades can be also given angular setting. Kaplan turbine runner has four to six blades and no shroud ring.
Tangential velocity component is provided by guide vanes. It is assumed that axial velocity flow at inlet and outlet remains constant throughout the duct.
- The direction of flow of water through the runner is parallel to the axis of rotation.
- Velocity of flow is constant
- The discharge is generally radial
Advantages of Kaplan turbine:
- Kaplan turbine has a higher hydraulic efficiency.
- It is more compact and fast running than Francis turbine.
- Turbine rotor has 4 to 6 blades while Francis runner has 10 to 25 blades.
- it has pure axial flow whereas Francis turbine has mixed flow.
- Frictional losses are less in Kaplan turbine.
- In this turbine runner blades are adjustable; Remaining turbine has adjustable moving blades.
- Kaplan turbine has higher specific speed than Francis turbine.
- It is suitable for low heads.
- It is handles large discharge with low heads.