汽车冷却水泵小流量工况下非定常空化特性研究

Unsteady cavitation characteristics of automobile cooling pump at low flow rates

针对汽车冷却水泵的空化问题,对小流量工况下非定常空化特性及其对压力脉动的影响进行了研究。采用SST k-ω湍流模型和Zwart-Gerber-Belamri (ZGB)空化模型,对水泵在典型空化状态下的流场进行了数值模拟研究,得到了小流量工况下叶轮内的非定常空化流动特征和空泡的时空演变规律;对蜗壳上的压力脉动进行了频谱分析,得到了不同空化条件对压力脉动的影响;通过泵的空化实验,对数值模拟结果进行了验证。研究结果表明:随着空化余量的减小,各监测点压力脉动峰的峰值和主频幅值逐渐增大,特别是隔舌位置处的压力脉动变化最为显著;泵内的空泡表现为不对称分布,主要集中在叶片前缘位置以及后盖板靠近叶轮进口位置,并随着空化的加剧,空泡体积分数逐渐增大。

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.