Impact of Transient Gas Injection on Flow-Induced Noise in Centrifugal Pumps

The influence of inlet gas volume fractions on flow-induced noise in centrifugal pumps during the transition process of gas injection and the generation mechanism of noise in this process was studied. To this end, numerical simulations of the flow and sound fields as well as visual experiments of the flow field were conducted. The variation laws of the flow field, frequency-domain sound field, and time-domain sound field during the process were investigated. The relationship between the pressure pulsation and flow-induced noise was analysed in detail. The results indicate that it is more reasonable to consider the outlet gas volume fraction as the judgement criterion for the end of the transition process. The axial and blade passing frequencies are characteristic discrete frequencies in this process. The pressure pulsation and sound pressure level at the blade passing frequency are stable in the early stage of the process. Subsequently, they decrease first and then increase in the middle stage and return to a stable state in the final stage. The variation laws of the two exhibit consistency, indicating that the pressure pulsation directly induces a change in the sound pressure level. Furthermore, the injection of gas can weaken the disturbance effect of the blade.