Investigation of pressure pulsation induced by quasi-steady cavitation in a centrifugal pump

Abstract

To study the pressure pulsations induced by quasi-steady cavitation in a centrifugal pump, the pressure pulsations at the pump inlet and outlet were experimentally investigated with the development of cavitation. Moreover, the internal flow characteristics in the pump during the process were numerically determined. The numerical simulation results agreed well with the results obtained from the experimental test, verifying the accuracy of the numerical simulation. Furthermore, the cavitation-induced pump inlet and outlet pressure pulsations of the centrifugal pump were analyzed by wavelet analysis and fast Fourier transform, and the cavitation incipient point and occurrence of the unstable cavitation point were obtained. The results of both wavelet analysis and fast Fourier transform show that in the quasi-steady cavitation stage of the centrifugal pump at the design flow rate, the pump inlet and outlet pressure pulsations are significantly increased at twice the axial frequency, while the other axial frequency components are weak and the internal flow is stable. With the development of cavitation in the pump, the pump inlet and outlet pressure pulsations at the axial frequency and its multiples afford some obvious broadband pulsations. To investigate the mechanism of quasi-steady cavitation-induced pressure pulsation in the centrifugal pump, the dynamic mode decomposition was used for internal flow field analysis. The results show that different inflow states lead to obvious differences in the internal flow and unsteady flow structures. There are complex pressure pulsation characteristics dominated by different frequencies in the centrifugal pump. Blade passing frequency plays an important role in the entire flow field, and its mechanism has been analyzed. This research will provide experimental and theoretical support for quasi-steady cavitation recognition and help researchers improve the operation stability of the centrifugal pump.