高落差クロスフロー水車の部分負荷時に生じるノズル拡大流路における損失低減法に関する研究

抄録

In cross-flow water turbines, the flow channel between the casing wall and the guide vane in the downstream side becomes a diffuser when the guide vane opening is narrow. In the diffuser, energy loss is produced due to both the occurrence of flow separation and turbulence. In addition, the turbine cannot be applied in a high head because an increase in flow velocity causes cavitation at the narrow part of diffuser. Therefore, the authors propose an energy loss suppression method by sucking air from the hole opened on the wall of the upstream the diffuser. Through this study, it was confirmed that sucking air into the diffuser causes water flow separation, therefore suppressing energy loss. This was accomplished using CFD. In addition, it was noted that the total pressure distribution derived by two-dimensional jet flow theory corresponds almost to the one obtained by CFD.