To improve the operational stability of pump-turbines for wide-load conditions

the influence of the runner blade angle at the high-pressure edges on performance is examined. A detailed analysis of flow characteristics and vortex structures at three blade angles (zero

positive

and negative inclination) for both optimal and low-flow conditions is conducted. Results show that at the optimal operating point

three blades at different angles all feature insignificant differences in performance

while flow instability develops for low-flow conditions because the increased positive incidence angle at the runner inlet leads to severe flow separation on the blades’ suction sides. Additionally

certain axial vortex structures in the runner passage induce backflow

while the negative inclination angle effectively reduces vortex intensity and suppresses backflow

increasing the spacing between dual axial vortices

mitigating vortex interaction

and thereby reducing energy dissipation. Furthermore

low-frequency components of the vortex structure are weakened significantly

contributing to pressure pulsation suppression to a certain extent. Compared to zero and positive inclination angles

the negative angle helps broaden the operational range of pump-turbines in the turbine mode and enhances operational stability.