1. Special Pump System Technology National and Local Joint Engineering Research Center, Xi′an Aeronautical University, Xi′an, Shannxi 710077, China; 2. Institute of Water Resources and Hydro-electric Engineering, Xi′an University of Technology, Xi′an, Shannxi 710048, China
Abstract：To research into the cavitation characteristics of pumpturbine and the mechanism of induced flow instability, a method of cavitation numerical simulation in combination with model tests was used. The cavitation characteristics of pump turbine under different flow pump conditions were obtained, the structural characteristics of turbulent field in pump turbine under different cavitation coefficient pump conditions were explored, the correlation between cavitation and vortex in pump turbine was clarified, and the cavitation flow characteristics of pump turbine and its mechanism of interference instability with mainstream were revealed. The results show that under different discharge and cavitation coefficient pump conditions, the location and intensity of cavitation occurs with obvious differences. Under low discharge pump condition, the flow separation caused by the intense cavitation on the suction surface at the low-pressure side of the blade interferes with the main flow, and large areas of decurrent and eddy current are produced, which reduces the efficiency of the pump turbine. Under optimal operating condition and large discharge conditions, once the flow separation caused by cavitation at different positions of adjacent blades interferes with each other, a large range of backflow and eddy currents will be formed in the runner blade passage, resulting in a significant reduction in the efficiency and head of the pump turbine.
