Patent ID: 7128534

Claim:
A Francis turbine, comprising: a rotating shaft; a crown rotating with the rotating shaft; a plurality of blades circumferentially arranged on the crown, each of which includes an outer end as a leading edge; a band coaxially coupled with the crown by the blades; and a local maximum point existing between the crown and the band on at least one of the leading edges; wherein the rotating shaft, the crown, the blades, and the band as a whole are driven by water and rotate toward turbine direction during a turbine operation, wherein the leading edge has a band connecting point where the band and the leading edge are connected, wherein the leading edge leans toward the turbine direction from the band connecting point, wherein a circumferential distance in the turbine direction between the band connecting point and the leading edge is the largest at the local maximum point, wherein a distance P between the band and the local maximum point along a direction of a center axis of the rotating shaft is expressed, using a distance B between the band and the crown along the direction of the center axis of the rotating shaft, as (a) 0.25B≦P≦0.75B.