Abstract In order to study the pressure characteristics of Francis pump turbine flow in the peak zone inside, with a pumped storage station pump turbine as the research object, the whole flow channel unsteady numerical calculation was conducted for the model unit. Combined with the test data, the pressure fluctuation characteristics and flow characteristics at different positions in the hump flow under the pump operating conditions were aralyzed, and the impact of the flow on the unit pressure fluctuation characteristics was discussed. The results show that under the hump zone operating condition, the pressure pulsation at the volute outlet is mainly affected by the internal flow characteristics, at the same time is also affected by the upstream dual cascade role. The pressure time domain change periodicity at the minimal value point in the hump zone is disturbed. The pressure pulsation frequency between the runner and the guide vane is the low frequency, and the second frequency is 9 times and 18 times conversion frequencies. The pressure fluctuation amplitude increases with the flow rate decreasing. Cone tube pressure pulsation is the low-frequency pressure pulsation. The upstream pressure fluctuation of cone tube is greatly influenced by the dynamic interaction of the downstream runner-tail water pipe at the minimal value point in the hump zone, and there appears the pressure fluctuation of the high-frequency component
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