Abstract: Wide-load operation in the turbine mode is increasingly required for pump turbines in pumped storage plants, yet the pressure pulsations in the turbine intensify notably under small-opening, low-load conditions, posing a potential threat to unit safety and stability. Using the pulsation tracing network (PTN) method, this study examines a pump-turbine with a five-long and five-short blade runner, focusing on analysis of the pressure pulsation characteristics in its vaneless section under different heads, different guide vane openings, and different loads in the turbine mode. The results reveal complicated pressure pulsation components in the vaneless section, including typical frequencies such as 0.33fn, 1fn, 3fn, 5fn , and 10fn (fn for one tenth of the blade passing frequency), and the ones of 10fn and 5 fn exert the most significant influence. The phase characteristic analysis further indicates the dominant frequency pulsations propagate upstream and downstream, affecting flow stability throughout the full passage. These findings provide valuable insights for optimizing pump-turbine runner design to enhance wide-load operational performance.

Key words: pressure pulsation, pump turbine, power generation, vaneless section, pulsation tracking network