5 Mw Francis Hydro Turbine/Francis Turbina Generator 500kw Water Francis Turbine

Francis Water Turbine

The original Francis turbine has been modified from time to time to improve its efficienty, and today, an efficienty of more than 93% has been reached. Francis turbine is a versatile one and can work over a very wide range of heads from 25m onwards to 550m. This is a reactin type of turbine where water is admitted at high pressure into the runner, and pressure energy is converted into mechanical energy, because of the reaction of water when travling over the curved vanes. As the pressure inside the turbine varies, Francis turbine is also called a variable pressure turbine.

Runner shape depends on the head, output and specific speed of a turbine. Runner vanes numbers depends upon head, output and rotational speed of the runner. It may vary from 10 to 20. This number may be less than the number of guide vanes. To prevent water under pressure from bypassing the runners and finding its way directly from the guide vane to the draft tube, sealing rings called labyrinth rings are provided at the exit of the runner on the outer face to the band.