Abstract: Flows of viscous oil in a centrifugal pump impeller with large discharge and small wrapping angles of blade are measured by using a two-dimensional laser Doppler velocimeter at the best efficiency and part-loading points, respectively, and the features of the flow are analyzed. The tested results show that a wake separated is found near the suction side and a jet does not exist near blade pressure side, so that the wellknown jet/wake flow model is not found in the impeller tested. The range that the wake covers is enlarged while the pump working condition is changed from the best efficiency to the part-loading points. The wake separated should be weakened or eliminated to improve the hydraulic performance while the impeller handling viscous oils.

Key words: Centrifugal pump, Flow, Impeller, Viscous oil