Experimental and Computation Investigation of the Rotating Instability in a Centrifugal Pump Impeller

The paper reports on experimental and numerical investigations aimed at understanding the mechanisms of rotating instabilities in a centrifugal pump. The phenomena of rotating instabilities in the impeller were first identified with an experimental study. Afterward an unsteady numerical analysis was applied to confirm the phenomena and to detail the mechanisms behind them. The experimental study was conducted with high-response pressure measurements at three planes, at the pump, and at diffuser inflows. The numerical investigation, for the entire pump, was performed with an unsteady 3-D Navier-Stokes method. Turbulence was modelled both by the k-ω transport equations model and Reynolds Stress Model. The effects of the tip leakage flow were considered by meshing the tip clearance between rotor blade and casing The current study reveals that a vortex structure forms near the leading edge plane. The formation and movement of this vortex seem to be the main causes of unsteadiness when rotating instability develops. This unsteady phenomenon was highlighted both at design flow rate and at low flow rates. The azimuthal distributions exhibited no significant uniformities and the amplitude of this non-uniformity was sensitive to the flow rate.