离心泵压力脉动测试关键问题分析

分析了离心泵进口区域、压水室区域和出口区域压力脉动的特点,提出了用于压力脉动试验研究的测点布置方案,尤其是蜗壳隔舌区测点布置方案.分析了采样频率和采样时间对测试结果的影响,得出采样频率主导频域的频率范围,采样时间主导频域的频率分辨率.在给定频率分辨率的前提下,结合采样定理和FFT方法特点,建立了普遍适用的离心泵压力脉动测试采样频率和采样时间选取公式.比较了运用5种不同窗函数进行FFT分析时所产生的频域分辨率和频率幅值的差异,发现矩形窗函数比其他窗函数在捕捉主频脉动频率及保持频率幅值不失真方面具有一定的优势.

Key issues in pressure fluctuation experiments for centrifugal pumps

Based on the analysis of pressure fluctuations at different flow regions in centrifugal pumps,measuring point arrangements on suction chamber,volute casing and delivery pipes are proposed.Especially,the distribution scheme of measuring points near volute tongue area was discussed in details.The impacts of sampling frequency and sampling time on the experimental results were analysed.The results show that the sampling frequency determines the range of frequency domain,and sampling time determines the frequency resolution.Combining the sampling theory with features of the FFT method,two constraint equations for determining sampling frequency and sampling time are established.Five window functions used for FFT analysis were compared by means of their frequency resolutions and amplitudes.The rectangular window function is recommended because of its advantage in the capturing the main frequency and keeping its amplitude lossless for centrifugal pumps.