| 摘要 |
PURPOSE:To prevent a discharge ring from the damage caused by cavitation by the use of the necessary minimum of stainless steel by using the stainless steel preponderantly in the area positioned above a water turbine shaft of a discharge ring. CONSTITUTION:An area of a discharge ring 31 at least in contact with water current is damaged by the cavitation caused near the exit on the periphery of a runner vane. It is shaped into a ring by stainless steel material 6, and prevented from the damage caused by the cavitation. In this case, degrees of the generation of the cavitation are different between the upper and the lower ends of the runner. The cavitation is easily generated in the upper end 1a, and difficult to be generated in the lower end 1b. Therefore, the discharge ring 31 is constructed of stainless steel material 31a only in the exit rear stream part of the upper half of a peripheral part 3a horizontally divided into two in a runner vane 3. This construction permits to keep the use of expensive stainless steel material at the necessary minimum. |
