Abstract: The internal flow in a centrifugal pump impeller is measured accurately by using two-dimensional Laser Doppler Velocimeter (LDV) at best efficiency and part-loading points, respectively, as the pump handing the viscous oil whose kinematic viscosity is 48 mm2/s. The measurement shows that there is a wide wake near blade suction side and not a jet near blade pressure side so that the internal flow in a centrifugal pump impeller dose not present the well-known wake/jet flow model, but a wake/primary flow model. The wake is located at two corners of shroud and hub with the suction side, and covers the whole suction side. While pump work condition moves from the best efficiency point to part-loading point the wake will be enlarged.

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