Analysis of the unsteady flow velocity fields inside the impeller of a radial flow pump: PIV measurements and numerical calculation comparisons

PIV measurements were performed at mid hub to shroud section inside the impeller of a vaned diffuser pump model working with air. The measurements were restricted to the outlet section of the impeller where the diffuser blades interacted with the impeller flow. Each PIV measuring plane was related to one particular impeller blade to blade channel and analysed according to different relative positions of the vaned diffuser. Two frame change models were considered: the so-called frozen rotor approach for different impeller passage positions relative to the vaned diffuser and a fully unsteady calculation of the whole pump. Comparisons between numerical and experimental results are presented and discussed for a specific mass flow rate corresponding to an off-design point for the impeller and a design point for the vaned diffuser.