Influence of leading-edge cavitation on impeller blade axial force in the pump mode of reversible pump-turbine

The variation of blade axial force of pump-turbine, which may cause instability on impeller shaft system, can be influenced by cavitation. However, the mechanism of this phenomenon is still not clarified. In this study, numerical simulation and experimental research are combined to investigate the influence of leading-edge cavitation on impeller blade axial force in the pump mode of reversible pump-turbine. From no cavitation to critical cavitation, the axial force increases first and then decreases rapidly. The largest increase is 5% and the largest decrease is 13%. Under different flow conditions, the cavitation pattern of blade leading-edge changes differently. With the increase of flow rate, flow separation and pressure drop gradually move from suction side to pressure side. The change of blade axial force caused by the change of blade loading is essentially related to the cavitation occurring on the pressure surface or suction surface. The variation of axial force with cavitation development is similar but the mechanism is different under different conditions. This study reveals the effect of cavitation on blade axial force and its mechanism. The research results can provide reference for improving the operation stability of pump turbine unit.