Francis turbine

Abstract

A Francis turbine with an improved shape of blades, which can reduce a circumferential velocity component generated in the flow downstream of the blades in a condition of a partial load operation, or reduce the secondary flow around the blades, is provided. A Francis turbine comprises a crown, a plurality of blades, and a band. The crown can rotate around a rotating axis. The blades are circumferentially arranged on the crown, each of which including an inner end as a trailing edge. The band is coaxially coupled with the crown by the blades. A distance Rc can be defined as a distance between the rotation axis and an end by the crown side of the trailing edge. A distance Rb can be defined as a distance between the rotation axis and an end by the band side of the trailing edge. The distance Rc and the distance Rb satisfy 0.2 ≤ R c R b ≤ 0.4 .

Dependencies are inferred from the claim text.