Simulation analysis of energy characteristics of flow field in the transition process of pump condition outage of pump-turbine

The pump-turbine is the heart of a pumped storage power plant. This study combines numerical simulations with experiments to investigate the flow stability, energy loss in the main flow area and their interconnection in the transition process of the double-row cascade and runner chamber of the pump-turbine, when the pump-turbine is operated under pumping conditions with a sudden power failure and the guide vane refuses to close. The results show that the overall flow pattern of the transition process is extremely unstable, and the flow state is presented as smooth-disturbed-smooth-disturbed, with the maximum vorticity difference(Delta omega) of 696756 s-1 in the neighboring working conditions; the maximum entropy production rate of the double-row cascade and runner chamber in the braking process has a similar trend in the vorticity change trend, and the rapid change of the flow pattern of the internal fluid causes the sharp change of the entropy production in the pump-turbine; The maximum entropy production rate in the runner chamber is of the order of e6, which is much higher than that in the other regions, and the poor flow phenomenon caused by the runner is the main reason for the energy loss.