Blockage and Distortion Effects on a Vane Island Type Diffuser Performance of Centrifugal Pumps for Various Flow Rates

Experimental investigation of mean flow velocity and pressure inside the vane-island type diffuser passage of a laboratory centrifugal pump model is presented in this paper. A three-hole directional probe was used to investigate hub to shroud flow properties at diffuser leading and trailing edge planes and at the mid-section between suction and pressure sides along the diffuser passage. All these measurements have been performed for five different flow conditions. The flow structures at the inlet section of the diffuser and along with the passage were analyzed in detail, with a focus on the flow distribution and the pressure recovery evolution of different diffuser part. Block age and distortion effects are analyzed using existing published Particle Image Velocimetry (PIV)measurements in the outer part of the impeller and around the diffuser throat in order to get a better understanding of the overall performances and local flow structures of such a diffuser design.