Comparison of Flow Fields in a Centrifugal Pump Among Different Tracer Particles by Particle Image Velocimetry

Abstract

This paper presents an experimental investigation of the flow fields in a centrifugal pump by particle image velocimetry (PIV) technique with two different tracer particles, all designed for the same operating point. In order to systematically analyze the tracking characteristics of tracer particles once used in centrifugal pump by Basset–Boussinesq–Oseen (BBO) equation, aluminum powder (AP, with high density ratio and small diameter) and hollow glass spheres (HGS, with neutral density and large diameter) were selected. The velocity fields obtained for AP and HGS were presented and compared, in order to enhance the understanding of their tracking properties in rotating impeller. The results show that AP and HGS give nearly the same phase-averaged velocity fields except at two small regions. BBO extended equation by the phase average theory in a centrifugal pump was applied to explain the first difference, namely, why the velocity of HGS is higher than that of AP in the low-speed zone. In addition, the mean vorticity distributions for AP and HGS show high strength velocity micelles with different directions of development and dissemination, which causes the second difference in energy exchange. As a consequence, HGS tends to conglomerate closer to the pressure side (PS) near the impeller outlet than AP