Coherence theory-based analysis of time–space coupling between internal flow noise and pulsations in axial pump under blockage

Abstract Safety barriers are commonly installed at the inlet passage entrances of large and medium-sized low-lift pump stations to intercept floating debris and ensure the safety of humans and animals. To clarify the variation of internal pressure pulsations and hydraulic noise of axial-flow pumps when the safety barrier is blocked, numerical simulation of a vertical axial-flow pump device with a safety barrier at 0.3 blockage ratio under different flow conditions was conducted using the VLES k–ω model. Fast Fourier transform was applied to transform the time-domain signals of both pressure pulsations and hydraulic noise. The study explores the correlation between pressure pulsations and hydraulic noise using coherence theory. The results show that, at all flow conditions, the amplitude of pressure pulsations and hydraulic noise increases from hub to rim at monitoring points at impeller inlet, outlet and guide vane outlet. The pressure pulsation time-domain amplitude range increases from (−0.008 to 0.007) to (−0.195 to 0.131), while frequency-domain amplitude range increases from 0.002–0.013 to 0.003–0.092. The average sound pressure level of hydraulic noise increases from 92.98–106.49 to 107.64–114.41 dB. The main frequencies of pressure pulsations and hydraulic noise were concentrated around fBPF, with secondary frequencies observed at 8fn and fn. Strong correlations (γ2 ≥ 0.9) between pressure pulsations and hydraulic noise mainly occurred in the vicinity of fBPF and fn.