Rotordynamic Forces on a Four 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 four-bladed, tapered-hub, variable-pitch inducer, designated as DAPAMITO4. The forces acting on the impeller have been measured by means of a rotating dynamometer mounted just behind the inducer. The roles of the imposed whirl motion of the rotor, flow coefficient, cavitation number and liquid temperature have been investigated. The destabilizing role of cavitation has been confirmed. The experimental results are consistent with previous findings obtained by the authors, as well as with former data published by Caltech researchers. The observed dependence of the tangential and normal components of the rotordynamic force on the whirl-to-rotational speed ratio does not follow the quadratic functional behavior often assumed in the open literature. Rotordynam...