Experimental investigation of pressure instabilities affected by cavitation for a double-suction centrifugal pump

Abstract

Cavitation is a common fault which has a close relationship with pressure instabilities in centrifugal pumps. In order to investigate the hydroacoustic response to cavitation phenomena, a pressure fluctuation experimental is carried out on a double-suction centrifugal pump. Frequency spectrum analysis and time-frequency joint analysis of pressure fluctuations in semi-spiral suction chamber and volute casing are presented based on fast Fourier transform (FFT) and adaptive optimal-kernel time-frequency representation (AOK TFR) methods. The results show that in semi-spiral suction chamber, as the available NPSH value continuously decreases, the frequencies affected by cavitation transfer to a lower frequency range and become relative higher concentrate in time-frequency representation. In volute casing, blade passage frequency (BPF), specific frequency at 1/2 of blade passage frequency (147 Hz) and some frequency bands are well captured. The amplitudes of BPF and BPF/2 are shown to have a reasonable dependence on available NPSH value, though the measuring location relative to volute tongue should be taken into account. Strong pulsation characteristics are observed on relative low available NPSH value conditions. Pressure fluctuation at impeller rotating frequency is shown to be sensitive with cavitation process, of which the amplitude sharply increases at first and then decreases. © Published under licence by IOP Publishing Ltd.