离心泵内空化流动诱导非定常激励特性

Characteristics of Unsteady Excitation Induced by Cavitating Flow in Centrifugal Pumps

空化流动诱导的非定常激励是引起泵振动噪声的主要因素之一,为研究其特性,运用完整空化模型和混合流体两相流模型,对比转数为86的离心泵流道内部的空化流动进行非定常数值计算。结果表明,空化的初生位于叶片背面进口边附近,随着进口压力的下降,空泡不断向叶轮出口方向扩散,当空化现象严重时,流道内会出现低速漩涡区;流场中压力脉动频率存在明显离散特性,叶片通过频率下的脉动幅值较大;流场内压力脉动强度大小会随着空化发展程度的强弱相应发生改变,空化越严重,压力脉动越强烈,且叶轮所受径向力合力大小及监测时间内始末两时刻瞬时径向力差异也越大,同时非定常径向力波动幅度也较大;空化的发展还会导致轴向力的大幅增加,对泵运行的稳定性及泵轴的安全性造成影响。

Unsteady excitation induced by cavitating flow is one of the main factors causing the vibration and noise of the pump. In order to study the characteristics of unsteady excitation, the unsteady numerical simulation of the cavitating flow in the flow-passage of a centrifugal pumps is carried out by using the full cavitation model and the mixed two-phase flow model. Simulation results indicates that the cavitation bubbles generate at the suction side of blades near the leading edge, the region of bubbles extends with the reduction of inlet total pressure. When cavitation becomes serious, low-speed vortex is observed in the flow-passage. The frequency of the pressure fluctuations has the obvious discrete characteristics and the blade passing frequency dominates the pressure fluctuations. Along with the development of cavitation, cavitating flow can induce the increase of pressure fluctuation amplitude in the flow-passage, and there is a corresponding relationship between them. The cavitation can also induce the increase of unsteady radial force fluctuation amplitude and substantial increase of axial force. So cavitation affects operation stability and reliability of pumps.