Numerical simulation of the characteristics of flow-induced noise in a helical-axial pump

Abstract:

To identify the flow-induced noise sources in a helical-axial pump and analyze the influence of the unsteady flow on the flow-induced noise, a numerical simulation analysis of the flow-induced noise in the pump was conducted using a combination method of computational fluid dynamics (CFD) and acoustic finite element method (FEM). Firstly, the 3D unsteady flow within the pump was simulated using the shear stress transport (SST) turbulence model in ANSYS CFX to obtain the pressure pulsation characteristics of the flow field. The pressure pulsations on the solid walls were treated as excitation sources, and the flow-induced noise field in the pump is numerically calculated using the FW-H equation with the software of LMS Virtual Lab. In order to identify the noise source location, the focus was put on the frequency domain characteristics of flow-induced noise and the contribution of different components and regions to noise. Finally, based on the temporal signal correlation and coherence theory, the spatial-temporal correlation of the pressure pulsation signal on the impeller blade surface was deeply analyzed to reveal the flow characteristics and noise contribution mechanism of the key noise source region. The results indicate that, compared with the downstream of the diffuser, the flow-induced noise at the upstream of the impeller is greater and exhibits a slower attenuation with increasing frequency, with the highest noise contribution occurring in the frequency range of 0~3 000 Hz. The maximum sound pressure peak appears at the blade passing frequency. The total sound pressure level of the rotating source at the monitoring point is 25.4 dB higher than that of the stationary source, with the suction surface of the blade generating more noise than the pressure surface, particularly in the first 50% chord length region, which contributes significantly to the overall noise. Spatial-temporal correlation analysis of pressure pulsation signals at different positions on the suction surface of impeller blades reveals that the pressure pulsation in this region primarily originates from boundary layer separation.