水力発電用水車の小型試験装置における部分流量・過大流量キャビテーションサージに関する研究

抄録

Model tests and CFD were carried out to find out the cause of cavitation surge in hydraulic power plants. In experiments the cavitation surge was observed at flow rates higher and lower than the swirl free flow rate, both with and without a surge tank placed just upstream of the inlet volute. An unsteady CFD was carried out with two boundary conditions：(1)the flow rate is fixed to be constant at the inlet volute, (2)the total pressure is kept constant at the volute inlet, corresponding to the experiments without/with the surge tank. The surge was observed with both boundary conditions at both higher and lower flow rates. Discussions as to the cause of the surge are made based on additional tests with an orifice at the diffuser exit, and with the diffuser replaced with a straight pipe.