Experimental and Numerical Investigations of the Noise Induced by Cavitation in a Centrifugal Pump

Abstract

The noise induced by cavitation in a centrifugal pump is investigated by collecting the noise of the centrifugal pump under different available net positive suction heads (NPSHa) in the rated flow through experiments. Experimental results are combined with numerical calculations to establish the relationship between cavitation degrees and noise. Firstly, the collected noise signal is denoised using the independent component analysis (ICA) method, and combined with time domain, Fast Fourier transform (FFT), wavelet transform (WT), and spectral proper orthogonal decomposition (SPOD) methods to analyse the characteristics of cavitation noise signal after noise reduction. After being denoised by ICA, the noise signal can effectively reflect the inception and development of cavitation. In the frequency domain, the typical frequency band of noise induced by cavitation is 2 ~ 8 kHz. During severe cavitation, the amplitude of the shaft and blade frequency in the low-frequency band (0 ~ 600 Hz) gradually decreases until they become low-frequency broadband signals. In the time–frequency domain, when cavitation develops to an unstable cavitation state, the 0 ~ 1 kHz noise amplitude fluctuates irregularly. Finally, the coherent structure of cavitation noise feature signals is established using the SPOD method. Higher-order modes 3 and 4 can capture the characteristic changes of the centrifugal pump cavitation noise at different NPSHa.