空化对低比转速离心泵内流声特性的影响研究

Investigation on flow and noise characteristics affected by cavitation in low specific speed centrifugal pump

为了研究空化对低比转速离心泵内流声特性的影响,采用数值模拟和实验测量相结合的方法,研究了其在不同空化数下的压力脉动和流动噪声特性,并对典型位置处的压力脉动频域特性及声压频率响应进行了重点分析。结果表明:随着空化的发展,泵内低频及宽频脉动加剧。临界空化时,1/6倍转频成为了叶轮进口处的压力脉动主频,蜗壳区域内叶频虽仍为压力脉动主频,但1/6倍转频已成为了较为显著的次频。动静干涉作用引起的压力脉动是流动噪声的主要噪声源。空化诱导的噪声为宽频噪声,且主要集中在1000~2000 Hz高频段内。叶轮旋转偶极子声源作用下的特征频率处声压级随着空化的发展而下降;蜗壳偶极子声源作用下的特征频率处声压级随着空化的发展而增大,且叶频倍频处特征频率逐渐被淹没在其高频宽频段中。该研究可为低比转速离心泵中探究流声特性变化规律、降低因空化而加剧的振动和噪声提供必要的依据。

To understand the effect of cavitation on the flow acoustics of a low specific speed centrifugal pump,this study examines the characteristics of pressure fluctuation and flow noise under different cavitation numbers by combining numerical simulations with experimental measurements,focusing on analysis of the frequency domain characteristics of pressure fluctuations and the frequency responses of sound pressure at typical positions.The results show that as cavitation develops,low-frequency broadband fluctuations in the pump are intensifying.At critical cavitation,the 1/6 rotation frequency becomes dominant in pressure fluctuations at impeller inlet and in the volute region it becomes a significant secondary frequency while the blade passing frequency remains dominant.Pressure fluctuations caused by rotor-stator interaction is the major source of flow noise,and noises induced by cavitation are broadband concentrating on a high-frequency band of 1000-2000 Hz.As cavitation develops,the sound pressure level at the characteristic frequency drops under the action of impeller rotating dipole sound source while it rises under the action of volute dipole sound source,and the characteristic frequency at the high harmonics of blade passing is gradually submerged in a high-frequency broadband.This study lays a basis for further study of the flow and sound behaviors and for reduction of cavitation vibration and noise in low specific speed centrifugal pumps.