The influence of casing treatment on the performance of a centrifugal pump

Abstract

Centrifugal pumps may run under off-design conditions such as low flows. Under such conditions, back-flow may occur at the impeller inlet and block a part of the flow path and cause energy loss. Casing treatment has been widely used in centrifugal compressors to improve their performance at low flow conditions, but there is little in the open literature on the effect of casing treatment on the performance of centrifugal pumps. In this paper, a SC100-200 centrifugal pump is studied with a casing treatment. First, the CFD method employed was described and verified by the experimental results of the pump. CFD indicates that the starting point of the back-flow is around discharge coefficient of 0.111 of the pump, and the back-flow intensity gradually increases with the decrease of flow rate reaching another critical point at discharge coefficient of 0.061 where the back-flow upstream traveling distance suddenly increases significantly. Then a casing treatment is created in the inlet end-wall and front cover using a U-tube type configuration. The numerical simulation was carried and it is found that a part of the back-flow at the inlet and front-side cavity of the centrifugal pump is sucked to the U-tube of the casing treatment and returns to the pump inlet, the back-flow and entropy production at the impeller inlet are reduced, and the head and efficiency of the pump is little affected. Further research shows that the longer the length of the U-tube is, the stronger the suction effect will be, and the smaller the back-flow of the pump.