Abstract：In order to research the effect of pressure fluctuation caused by complicated flow inside centrifugal pumps at shut-off condition,based on the virtual technology and LabView,the pressure signal of centrifugal pumps was decomposed and the wavelet packet analysis was applied to extract the feature spectrum and establish different frequency bands.The experiment was carried out to test the analysis results.The analysis results show that the pressure pulsation at shut-off condition is irregular and non-cyclical,and low-frequency pulsation plays an important role.With the flow decreases,the amplitude of the shaft frequency first increases and then decreases.Backflow appears when centrifugal pumps operate at low flow rate to shut-off condiftions and the wavelet packet reconstruction coefficient changes,and it could be concluded that backflow exert significant influence at low frequency.The amplitude and strength at shut-off condition with enhancement on shaft frequency.The inlet backflow of centrifugal pumps at shut-off condition is braided backflow.The validating test results show that different frequency corresponding to different unsteady flow can be identified based on wavelet packet,which will improve the diagnosis of the inner flow of centrifugal pumps at shut-off condition.
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