Numerical investigation of hump characteristic improvement in a large vertical centrifugal pump with special emphasis on energy loss mechanism

This study aims to numerically investigate the reasons for the hump characteristic improvement of the large vertical centrifugal pump (LVCP) optimized model and thus explore the methods for inhibiting the hump of LVCP. The special emphasis was on the study of the vortex-induced energy loss mechanism of LVCP under stall conditions based on entropy production theory combined with Ω vortex identification technology. The performance curves showed an increased hump margin and a decreased range of hump region for the LVCP optimized model. The results of entropy production and vortex identification analysis showed that the hump of LVCP was mainly caused by the unstable growth of ΔSPRO. The reduction in ΔSPRO,D' made a significant contribution to the LVCP hump characteristic improvement. The stall vortices (SV) in the vaned diffuser dominated the energy loss. Moreover, the backflow at the elbow pipe outlet and impeller inlet regions also caused significant energy loss. The matching optimization between the flow angle in the vaneless region and diffuser inlet vane angle led to the decrease of energy loss and SV scale in the diffuser, which was the key reason for the hump characteristic improvement of the LVCP optimized model. Meanwhile, the better flow pattern on the large section side of the optimized volute resulted in the energy loss reduction which increases the hump margin.