离心泵小流量工况不稳定空化特性研究

为了研究离心泵小流量工况不稳定空化特性,通过数值模拟和试验,研究了离心泵小流量工况不同空化程度泵的内流特性及泵进出口压力脉动特性。结果表明:小流量工况下,蜗壳隔舌与叶轮间的动静干涉对离心泵内部不稳定流动具有重要影响,叶轮流道内受空化影响所产生的漩涡与受蜗壳隔舌影响所产生的漩涡的流动方向相反。随着空化的发展,离心泵进口压力脉动的主频由2倍轴频逐渐向低频段迁移,且存在一定的波动;泵进口压力脉动存在于2倍叶频处的峰值,随着空化发展到一定程度而消失;受叶轮与隔舌动静干涉的影响,泵出口压力脉动的主频为叶频,在2倍轴频处存在波动较大的峰值;泵进出口压力脉动的宽频脉动随着空化余量的降低存在明显变化。

Investigation of Instabilities of Cavitation at Low Flow Rate of Centrifugal Pump

In order to investigate the instabilities of cavitation at low flow rate of centrifugal pump, with the development of cavitation in a centrifugal pump, the characteristics of the internal flow, inlet and outlet pressure pulsations of the pump were researched through numerical simulation and experiment. It was found that the rotor stator interaction between the volute tongue and impeller made a significant influence on the internal flow instabilities of a centrifugal pump under low flow rate condition. The vortexes generated by the influence of cavitation and volute tongue presented in opposite directions. The dominant frequency of the pump inlet pressure pulsations was two times shaft frequency, which migrated to low frequency with certain fluctuations with the development of cavitation. The peak which existed at two times blade passing frequency of the pump inlet pressure pulsations vanished when the cavitation developed to a certain degree. The dominant frequency of the pump outlet pressure pulsations was the blade passing frequency resulted from the rotor stator interaction between the volute tongue and impeller. The peak which existed at two times shaft frequency presented intensive fluctuations. The broadband pulsations of both pump inlet and outlet pressure pulsations changed obviously with the decrease of available net positive suction head.