船用离心泵压力脉动与振动信号的相干分析研究

非定常流动是引起泵振动的主要因素之一,为了明确压力脉动与振动之间的关联关系,搭建了闭式实验系统,对一台船用离心泵进行压力脉动和振动的同步测量。基于快速傅里叶变换获得了各监测点压力脉动、基脚振动信号的频谱特性及功率谱特性；通过计算压力脉动信号与振动信号的相干函数,并通过比较不同测点的相干系数大小,分析了压力脉动对振动的贡献。结果表明,压力脉动与振动均在轴频、叶频及其高次谐波等离散频率下能量突出；不同频率下各测点的压力脉动对泵振动的影响存在差异,其中进口压力脉动在600-700Hz及900-1000Hz频段对振动影响最大；隔舌压力脉动在0-600Hz及700-900Hz频段对振动影响最大；出口压力脉动在轴频的高次谐波等个别频率处对振动有一定影响。相干分析可作为建立压力脉动与振动信号之间关联关系的一种有效手段,由此为进一步离心泵内部流场改善及减振提供参考。

Identification of Relationship between Pressure Fluctuation and Vibration in a Centrifugal pump Based on Coherence Analysis

Unsteady flow in the centrifugal pump is one of the main factors that induce pump vibration, in order to identify the relationship between pressure fluctuation and vibration, both pressure fluctuation and vibration signals were measured simultaneously in a centrifugal pump. Frequency spectrum and power spectrum density (PSD)analyses were performed on the signals obtained at different locations based on fast Fourier transform. By calculating the coherence function and comparing the coefficient value of two signals at different monitoring points, the contribution of pressure fluctuation to vibration were obtained. The results show that the behavior of pressure fluctuation at different frequencies have certain effects on the vibration for each studied locations: pressure fluctuation of the inlet-pipe has the largest effect on pump vibration at the range of frequencies between 600Hz and 700Hz as well as 800Hz and 1000Hz; and pulsation near the volute tongue zone dominated at the range of frequencies between 0 and 600Hz as well as 700Hz and 900Hz; while the signals at the outlet section just impact at several separate frequencies on pump vibration. It turned out that Coherence analysis could act as an effective method to develop relationship between pressure fluctuation signals and vibration signals, thus supporting the further study of inner flow and vibration reduction in a centrifugal pump.