| 摘要 |
PURPOSE:To reduce the hydraulic loss of a water turbine produced on the inside of a runner, by reducing the water flow rate by decreasing the opening of guide vanes temporarily in low-output operation of the water turbine, and thereby lowering the water surface under the runner for feeding air to the inside of the runner. CONSTITUTION:In low-outut operation of a water turbine, the water flow rate is reduced temporarily by decreasing the opening of guide vanes 6. By thus lowering the water surface 11, a hollow passage is formed on the downstream side of jet flow 12 and air is supplied to the central portion of a runner 1. In shifting the point of operation in the low-output range to a point of operation in the high-output range, the hydraulic loss produced on the inside of the runner 1 can be reduced by feeding air sufficiently to the central portion of the runner 1. With such an arrangement, it is enabled to operate the water turbine at a high output (at a high efficiency). |
