Time-frequency characterization and energy distribution of fluid pressure pulsation of a centrifugal pump in the low-frequency domain

In order to explore the time domain and frequency domain characteristics of the pressure pulsation signal of centrifugal pumps in the low-frequency domain, the pressure pulsation data obtained from a centrifugal pump through testing are analyzed by using the method of complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and Hilbert transform. The results show that the CEEMDAN method demonstrates the variation pattern of pressure pulsation signals in the low-frequency domain of intrinsic mode function (IMF) and reveals the difference of hydraulic energy among the frequency bands. The paper defines the normalized correlation coefficient to indicate that the flow rate and the spatial location are the important factors affecting the correlation between the original pressure pulsation signal and IMFs. The correlation coefficient is the largest at the flow rate of 40 m3/h. At the same time, IMF7 and IMF8 contain the basic information of the original pressure pulsation signal. Using the method of energy averaging process, the instantaneous frequency of IMFs in the low-frequency domain is used to conduct analysis. It is proved that the pressure pulsation of the centrifugal pump at the low-frequency domain is the effect of the dynamic–static interaction between the impeller and tongue of volute. The relative standard deviation shows that the instantaneous frequency of pressure pulsation in the low-frequency domain is relatively concentrated with small fluctuations. With the increase in flow rate, the concentration of energy distribution shows a positive growth trend. The direction of energy distribution is consistent with the impeller rotational circumference. The energy of low frequency accounts for more than 50% and is concentrated in the long-wave region.