The Kaplan turbine is a hydraulic machine which is employed at hydroelectric power plant to drive a generator rotor for the generation of alternating current. It is hydraulic because it uses the kinetic energy of flowing water to produce a rotatory mechanical movement, which is transmitted to the rotor of a generator. ‘Hydrau-/hydro-‘ means ‘water’. This type of turbine is widely utilized in river and tidal flow schemes.
Main characteristics
The essential feature of the Kaplan turbine is that the water flowing through the runner does it in an axial direction. Its runner resembles a ship propeller, which is fitted with four or six blades. These blades are adjustable in pit so that they have the ideal angle for the flowing water. Thus, this type of hydraulic machine can keep its efficiency to this feature, which is the possibility of the runner performance to be improved by adjusting the angle of the blades. The blades can be adjusted by means of a lever arm within the hub.
The inlet spiral casing and the guide vanes of the Kaplan turbine have a layout and operation which are very similar to those of the Francis turbine. After leaving the guide vanes, however, the water flows into the axial direction before meeting the runner. Meanwhile, the bearing and the lubrication system layout is simple as the electrical generator installation, access, and maintenance are designed to be easy to work on.
Below, a diagram of a Kaplan turbine
