叶轮空蚀状态下离心泵振动特性分析

Vibration signal characteristics of centrifugal pumps with cavitation erosion impellers

空蚀是指空化过程中产生的空泡溃灭引起过流表面材料损坏的现象。为研究离心泵叶轮空蚀后的振动信号特征,选用IS-50-160-00单级单吸离心泵为试验对象,基于虚拟仪器技术搭建试验泵系统。测得离心泵空蚀条件下的振动信号,采用均方根(RMS)分析、峭度(K)分析两种统计方法对发生空蚀后的离心泵振动信号的平均能量、冲击波能量进行分析,采用短时傅里叶变换(STFT)分析了振动信号的时频域特性。分析结果表明:空蚀条件下整体来看基座方向和轴向方向振动幅值较大且都是无规则振动,而横向方向和纵向方向上的振动信号振幅相对较小;振动信号的能量随着流量的增大呈现先减小后平稳再增加的趋势,空蚀增加了振动信号的能量值;空蚀加剧了液体对离心泵的冲击使得振动信号峭度值增加,且基座方向峭度值大于3可作为空蚀故障的诊断参考标准;通过时频谱分析可知空蚀发生后流体可能对离心泵存在冲击波及冲击波导致的脉冲信号,且空蚀后产生了高频振动信号,高频带的振动信号可为离心泵空蚀故障诊断提供参考。研究叶轮空蚀后离心泵振动信号的特征有助于及时发现离心泵空蚀故障的发生,从而调整运行参数,以免造成严重后果。

Cavitation erosion is a phenomenon that surface material damages by the crumbling and failing of cavity.In order to investigate the vibration characteristics of a centrifugal pump after cavitation erosion,a single-stage single-suction centrifugal pump(type IS-50-160-00)was selected as the research object.A testing rig was built with the utilization of virtual instrument.The vibration signal of the centrifugal pump was measured.Statistical indicators of RMS and kurtosis were taken to analyze the average energy and shock wave energy of vibration signals.STFT was used to characterize vibration signals in time-frequency domain.The results show that there is a large extent variation of vibration amplitude in the direction of base and axis,and weak variation of vibration amplitude in the direction of radial and vertical.With the increasing of flow rate,the RMS of vibration signal falls at first,then keeps steady,and mounts at last when the flow rate is over the design point.The phenomenon of cavitation erosion causes the increasing of RMS and kurtosis value of vibration signal of the centrifugal pump.When the kurtosis value of vibration signal in the direction of base is over 3,it can be judged that the phenomenon of cavitation erosion occurs.It can be shown from the time-frequency spectrum that there is a shock wave and pause signals caused by the shock wave,which are reflected by the higher frequency band components of the vibration signal that can provide a reference to the diagnosis of the occurrence of cavitation erosion.Analyzing the vibration signal characteristics of centrifugal pumps with cavitation erosion impellers is of great significance to find out the cavitation erosion failure of the centrifugal pumps in time,and adjust the operating parameters to avoid serious consequences.