Abstract: A Francis turbine with an improved shape of blades, which can reduce cavitations generated on the surface of the blades or reduce the secondary flow around the blades, is provided. A Francis turbine comprises a rotating shaft, a crown, a plurality of blades, and a band. The crown can rotate with the rotating shaft. 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. The rotating shaft, the crown, the blades, and the band as a whole rotate toward a turbine direction during a turbine operation. A projected profile of the trailing edge on a perpendicular plane, which is perpendicular to a center axis of the rotating shaft, is curved toward a direction opposite to the turbine direction at least in the crown side.

Abstract: A Francis turbine with a improved shape of blades to reduce the secondary flow around the blades and improve the hydraulic efficiency is provided. A Francis turbine comprises a rotating shaft, a crown, a plurality of blades and a band. The band is coaxially coupled with the crown by the blades and the rotating shaft, the crown, the blades, and the band as a whole are driven by water and rotate toward a turbine direction during a turbine operation. On a leading edge of at least one of the blades, a local maximum point exists between the crown and the band. The leading edge leans toward the turbine direction from the band connecting point, where the band and the leading edge are connected. And, a circumferential distance in the rotating direction between the band connecting point and the leading edge is the largest at the local maximum point.

Abstract: A Francis turbine with an improved shape of blades, which can reduce cavitations generated on the surface of the blades or reduce the secondary flow around the blades, is provided. A Francis turbine comprises a rotating shaft, a crown, a plurality of blades, and a band. The crown can rotate with the rotating shaft. 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. The rotating shaft, the crown, the blades, and the band as a whole rotate toward a turbine direction during a turbine operation. A projected profile of the trailing edge on a perpendicular plane, which is perpendicular to a center axis of the rotating shaft, is curved toward a direction opposite to the turbine direction at least in the crown side.

Abstract: A Francis turbine with a improved shape of blades to reduce the secondary flow around the blades and improve the hydraulic efficiency is provided. A Francis turbine comprises a rotating shaft, a crown, a plurality of blades and a band. The band is coaxially coupled with the crown by the blades and the rotating shaft, the crown, the blades, and the band as a whole are driven by water and rotate toward a turbine direction during a turbine operation. On a leading edge of at least one of the blades, a local maximum point exists between the crown and the band. The leading edge leans toward the turbine direction from the band connecting point, where the band and the leading edge are connected. And, a circumferential distance in the rotating direction between the band connecting point and the leading edge is the largest at the local maximum point.

Abstract: An increment speed per unit time from the detected rotation speed of a water turbine or a pump turbine with an inlet valve is compared with a prescribed increment to deliver a close order to the inlet valve, when the increment becomes greater than the prescribed increment, for closing the inlet valve to a prescribed opening. Then, a fully open order to the inlet valve is delivered under the condition that neither an emergency shutdown order nor a quick shutdown order is issued to the water turbine or the pump turbine, when a speed governor performs a normal operation.

Abstract: In a Francis type pump turbine, for the purpose of switching the operation of a synchronous dynamoelectric machine from synchronous condenser operation wherein compressed air is admitted into a runner chamber to force down water level therein so as to cause a runner to rotate in air, to a synchronous generator operation, the air is released from the runner chamber and an inlet valve and guide vanes are completely or nearly completely closed. Then the inlet valve and guide vanes are gradually opened until a predetermined degree of opening is reached while maintaining the degree of opening of the guide vanes to be larger than that of the inlet valve. After the predetermined degree of opening, both the inlet valve and the guide vanes are gradually opened. But at this time the degree of opening of the inlet valve is maintained to be larger than that of the guide vanes. To switch from the generator operation to the condenser operation the same characteristic curves are traced in the opposite direction.