Abstract: To investigate the influence of the low pressure edge locations of short blades on the cavitation performance of a high-head pump-turbine with a splitter blade runner, three types of short blades are designed with the different locations according to the structural characteristics of splitter blade runners. The short blades are named as Scheme A, B, and C from the largest to smallest ratio of the diameter of low pressure edges at the upper crown over the runner diameter at the throat. A smaller ratio indicates the low pressure edges located further behind. We use a Rayleigh-Plesset cavitation model to simulate the steady states of the pump-turbine under three turbine conditions and two pump conditions, and compare the forms and energy of cavitation in the pump-turbine. The results show that at low flow rates, the cavitation performance of the runner is improved as the low pressure edges are moved backward, while at high and medium flow rates, Scheme B is better. In pump modes, the cavitation degree of the runner at high working heads is lowered first and then aggravated with the relative edge location moving backward, while the low pressure side in scheme A is most conducive at low heads. Considering both working modes, we conclude that Scheme B with a diameter ratio of 0.9487 is better in cavitation performance and its efficiency and working head are higher.

Key words: pump-turbine, short blade, low pressure edge location, cavitation, energy characteristics