Kaplan Turbine refers to the Axial Flow Reaction Turbine. For Axial Flow Turbines, the water passes through the runner alongside the course similar to the axis of rotation of the runner. Reaction Turbine refers to the water at the inlet of the Turbine retains Kinetic Energy and additionally Pressure Energy as well. In case of the Axial Flow Reaction Turbine, the shaft of the turbine has to be perpendicular. The lower end of the shaft is constructed bigger and is known as ‘Hub’ or ‘Boss’. The vanes are joined on the hub and thus the Hub turns as runner for axial flow turbine. The vanes on the Hub are changeable for Kaplan Turbine. The explicit speed (Ns) of Kaplan turbine extends from 300 to 600 and is a low head turbine.
Construction:
The chief parts of Kaplan Turbine are:
- Scroll Casing
The water from the penstocks sips through the scroll casing and then travels to the guide vanes. After that, from the guide vanes, the water turns through perpendicular and streams axially through the runner.
- Guide Vane Mechanism
The Guide Vanes are connected on the Hub.
- Hub
In case of the Kaplan Turbine, the shaft of the turbine has to be perpendicular. The lower end of the shaft is constructed bigger and is known as the ‘Hub’ or ‘Boss’. The vanes are immovable on the hub and thus Hub performs as runner in case of the axial flow turbine.
- Draft Tube
- The pressure at the end of the runner of Reaction Turbine is normally lesser in comparison than atmospheric pressure. The water at exit could not be directly discharged to the tail race. A tube or pipe of gradually growing area is utilized for liquidating water from the end of turbine to the tail race. This tube of augmenting region is known as the Draft Tube. One end of the tube is joined to the opening of runner although the other end is partially immersed beneath the layer of water in the tail-race.