Rotordynamic Forces on a Three Bladed Inducer

The present paper illustrates the results of an experimental campaign conducted in the CPRTF (Cavitating Pump Rotordynamic Test Facility) at Alta S.p.A. aimed at characterizing the rotordynamic forces acting on a whirling three-bladed, tapered-hub, variable-pitch inducer, designated as DAPAMITO3. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the flow coefficient, cavitation number, liquid temperature and of the imposed whirl motion of the rotor have been investigated. The linear dependence rotordynamic forces on the whirl eccentricity and the destabilizing role of cavitation have been demonstrated. The experiments confirm previous findings by Caltech researchers. The tangential and normal components of the rotordynamic force, as functions of the whirl-to-rotational speed ratio, do not show the quadratic functional behavior often assumed in the open literature. Unstable regimes and peak ...