Prediction of pressure pulsation in the vaneless zone of pump turbines during start-up process

The start-up of the pump-storage unit is widely recognized as one of the most critical operating conditions due to the high instantaneous amplitudes of pressure pulsations in the vaneless zone of the pump-turbine. These transient pressure pulsations generate significant dynamic forces on the runner, leading to substantial damage. Previous studies have primarily focused on the unsteady mechanisms of pressure pulsations during start-up cycles, often overlooking the importance of predicting pressure pulsations using existing measurements. This study predicts the amplitude-frequency characteristics of the pressure pulsations in the vaneless zone of the pump-turbine based on experimental data. The main components of the pressure pulsation including the blade-passing frequencies and the low frequencies are considered. The transient pressure pulsations in short durations assumed to represent steady-state pressure pulsations on the characteristic curves, achieving the final prediction. In the case study, only a large RMSE (0.7 m) was found between the prediction and the measurement over a short duration in the frequency domain, the prediction successfully captures the variation tendencies of main components in both time and frequency domains, demonstrating the effectiveness of the approach.