抄録
Turbine step characteristics have been found out in the course of new model development of low specific speed reversible pump-turbines. The step characteristic shows a fairly large decrease in performance curves of efficiency, discharge and power increasing in vibration and noise. Then, the effects of runner exit diameter, entrance angle and sweep back of runner vane upon this characteristic are studied, and flows near the exit of a runner are investigated by flow visualization and velocity measurement. As a result, it is clarified that, (1) the characteristic occurs in the model which has a small exit diameter and a large entrance angle, and is independent of sweep back, and (2) it is caused by the growth of reverse flow at the band side near the exit of the runner.
