Numerical investigation on the unsteady vortical structure and pressure pulsations of a centrifugal pump with the vaned diffuser

Abstract

To investigate the internal flow structures and the emanating pressure pulsations in a centrifugal pump with a vaned diffuser, the numerical method DDES (delayed detached eddy simulation) combined with a structured computational grid were employed to simulate the unsteady flow phenomenon of the model pump at the rated working condition. The vortical structures and pressure amplitudes at the blade passing frequency were mainly investigated. Results show that a significant difference, observed for pressure pulsations at the monitoring points from the suction side to the pressure side of the diffuser blade, and a high pressure amplitude is generated at the point near the suction side. The phenomenon is caused by the vorticity sheet interacting with the diffuser blade, and high turbulence is induced at the corresponding region leading to intense pressure pulsation. Evident attenuation of pressure pulsation is generated from the leading edge to the trailing edge of the diffuser blade. Significant vorticity sheets are formed around the trailing edges of the impeller and diffuser. Vortex street is generated at the diffuser trailing edge as indicated by the alternate shedding of positive and negative vortices and the horseshoe vortex is captured within the wake flow. Intense interaction is caused by the cutting impact of the volute tongue on the large scale vortices from the diffuser. The obtained results will contribute to a better understanding of unsteady flow and pressure pulsations in the centrifugal pump with a vaned diffuser.