Hollow blade for hydraulic turbine or pump

A runner for a hydraulic turbine or pump, comprising:

• a central hub;
• and
• a plurality of hollow blades radially extending from the hub at spaced intervals therearound, each blade having an inner edge fixedly secured to the hub and a distal outer edge, a leading edge and an opposed trailing edge, and a curved pressure side and an opposed curved suction side, at least one of the blades comprising:
• a curved pressure-side member including at least a substantial portion of the curved pressure surface and an opposed first inner surface, the pressure-side member having a curved hydrofoil shape including a generally flat upper portion and a three-dimensionally curved lower portion;
• and
• a curved suction-side member including at least a substantial portion of the curved suction surface and an opposed second inner surface, the suction-side member having a complementary curved hydrofoil shape including a generally flat upper portion and a three-dimensionally curved lower portion;
• wherein the curved pressure-side and suction-side members are fixedly secured together with the first and second inner surfaces facing each other, and wherein at least a portion of the first inner surface is spaced from at least a portion of the second inner surface to form a cavity within the blade, the cavity having a complex geometry and extending from between the generally flat upper portions to between the curved lower portions.

A hollow blade for a hydraulic turbine or pump, the blade including an inner edge and an opposed outer edge, a leading edge and an opposed trailing edge, and a curved suction surface and an opposed curved pressure surface, the blade comprising:

• a curved pressure-side member including at least a substantial portion of the curved pressure surface and an opposed first inner surface, the pressure-side member having a curved hydrofoil shape including a generally flat upper portion and a three-dimensionally curved lower portion;
• and
• a curved suction-side member including at least a substantial portion of the curved suction surface and an opposed second inner surface, the suction-side member having a complementary curved hydrofoil shape including a generally flat upper portion and a three-dimensionally curved lower portion;
• wherein the curved pressure-side and suction-side members are fixedly secured together with the first and second inner surfaces facing each other, and wherein at least a portion of the first inner surface is spaced from at least a portion of the second inner surface to form a cavity within the blade, the cavity having a complex geometry and extending from between the generally flat upper portions to between the curved lower portions.