クロスフロー水車の性能に及ぼす吸出しヘッドや有効落差の違いによる空気量の影響に関する研究

抄録

To prevent efficiency loss due to collision of water flow with the main shaft, atmospheric air is naturally sucked in through a hole in the casing of a cross-flow turbine using the negative pressure in the runner chamber. In this study, performance changes due to the flow-rate of intake air were investigated under two different effective head conditions. The values of the effective suction head NPSHa were adjusted so that the volume change of air in the runner would be the same for both head. The following results were made clear. Even if without suction air, a small gas phase area is formed in the runner due to air released from the water. If Q_air/Qw is greater than 0.04, the performance such as efficiency based on runner height and runner chamber pressure were almost same even if the air volume increases further.