Unsteady cavitation characteristics of automobile cooling pump at low flow rates
                                       ZHOU Xiaohong1, ZENG Weiyou1, CHEN Wei1, LUO Shijun1, GENG Ningyi2
(1.School of Science and Mathematics, Hubei University of Automotive Technology, Shiyan 442002, China;2.Zhejiang Institute of Geologic and Mineral Resources, Hangzhou 310007, China)

Abstract: Aiming at the cavitation problems of the automobile cooling pump, the unsteady cavitation characteristics and its effect on pressure fluctuations were numerically simulated. Based on SST kω model and ZwartGerberBelamri (ZGB) cavitation model, the internal flow field under some typical cavitations was analyzed, and the unsteady cavitating flow characteristics and bubbles' spacetime evolution were obtained. The effect on pressure fluctuations under different cavitation conditions were also obtained by spectral analysis. The simulation results were verified by the cavitation experiment. The results indicate that the pressure fluctuations of monitoring points in pump changed obviously when cavitation occurs. As the net positive suction head (NPSH) decreases, the peak values of pressure fluctuation and the amplitude of the dominant frequency increase, especially the monitoring point near the volute tongue. With the aggravation of cavitation, the bubble diffuses from the leading edge of the blade along the runner to the impeller outlet, showing a cyclical change and asymmetry distribution.

Key words: automobile cooling pump; unsteady flow; cavitation characteristics; pressure fluctuation; flow field analysis; numerical simulation