Experimental investigations on a centrifugal pump stage with and without a vaned diffuser

This paper presents experimental investigations in a centrifugal pump stage to verify the effect of the rotor-stator-interaction on the overall performance of the impeller as well as on the flow downstream of the impeller. Air was used as the test fluid. Steady and unsteady pressure measurements at different flow rates (q = 0.8 to 1.2) were carried out upstream and downstream of a radial impeller with a vaneless as well as a vaned diffuser For the latter, the radial gap between the leading edge of the diffuser vanes and the impeller outlet is 3% of the impeller tip radius. The radius of the measuring plane is the same for both diffuser types; halfway between the leading edge of the stator vanes and trailing edge of impeller vanes. For the vaned diffuser, the experiments were carried out at different circumferential positions between the suction and the pressure side of the stator vanes on the traversing plane. Ensemble-averaged distributions of the flow parameters (total pressure, velocity components etc.), integral parameters (total and theoretical head) and analysis of the pressure signals are presented. For the mean flow at each axial traverse position, the turbulent pressure fluctuations and the ensemble averaged pressure fluctuations are presented.