Unsteady flow characteristic analysis of a centrifugal pump under over-load operating conditions

Abstract

Unsteady flow phenomena, including flow separation, vortex flow, back flow and interaction between tip vortex and main flow, can occur in the centrifugal pump under over-load working conditions. Previous researches mainly focus on the flow characteristic under part-load working conditions, which is quite different from cases at over-load conditions. In this paper, flow characteristics are investigated in a centrifugal pump by CFD technology. The SST-CC turbulence model is adopted to perform steady simulations and the SAS-CC model is used in unsteady simulations of the centrifugal pump under 1.00QBEP - 1.45QBEP working conditions. Flow characteristic is proceeded with energy loss analysis by entropy method and pressure amplitude spectra. The results indicate that there appears a significant vortex core inside the impeller when the flow rate is larger than 1.28QBEP and the flow in the diffusing part and tongue region of the volute is complicated with several swirling vortices. The main frequency and amplitude are also investigated. There exists an evident low-frequency component near the volute tongue under over-load conditions, which is related to the vortices and flow separation inside the volute.