Francis turbine with ring around inner blade ring and hub - produces accelerated partial flow to reduce turbulence (SW060976)

摘要

A Francis turbine has an inner shroud (2), an outer shroud (6) and blades (4). As the water flows from the blades (4) vortices tend to form and the efficiency of the turbine is reduced. By fitting a ring (10) around the hub (12) such that the inner surface of the outerwall is parallel to the surface of the hub (12), the outlet area at (b) is less than the inlet area (a) so that the water flowing through the ring is accelerated. This increase in velocity prevents the formation of vortices on the hub (12) and eliminates a cause of energy loss and so increases the turbine efficiency.