The effect of blade outlet angle on the acoustic field distribution characteristics of a centrifugal pump based on Powell vortex sound theory

Abstract

Numerical simulation method based on Powell vortex sound theory is adopted to explore the mechanisms of acoustic field distribution characteristics of a centrifugal pump with different blade outlet angles. Results reveal that with the increasing of the angle, the fluctuation range of acoustic source at the tongue in time domain extends, which causes the same fluctuation characteristics of acoustic pressure. As the angle increases from 15° to 35°, the total acoustic source intensity (TASI) and total acoustic pressure level (TAPL) at the tongue increase by 1.68% and 2.54% on average under various rotational speeds, respectively. Additionally, the TASI and TAPL show the similar directivity characteristics under different angles, and the change of the angle has slight effect on the extremum distribution characteristics. Besides, the A-weighted average acoustic pressure level (Lp) and A-weighted average acoustic source intensity level (La) are adopted to describe the overall level of TAPL and TASI. When the angle increases from 15° to 35°, the La and Lp increase gradually and increase by 1.59% and 2.21% on average under various rotational speeds, respectively. The study reveals the acoustic source and acoustic pressure distribution characteristics in time and frequency domain qualitatively and quantitatively, and manifests that the distribution and variation patterns of acoustic source lead to those of acoustic pressure. The conclusions could lay a foundation for the empirical formula proposition between acoustic pressure and acoustic source.