Mechanism of the Occurrence of Rotordynamic Fluid Forces on a Closed Type Centrifugal Impeller in Whirling Motion

Abstract

Rotordynamic fluid forces and a mechanism of their occurrence were examined in experiments and computations for a closed type centrifugal impeller in whirling motion. The force on a front shroud was a main component of the rotordynamic fluid force. Velocity disturbances in a clearance between the front shroud and a casing were caused by an eccentricity of the impeller and a squeeze effect due to the whirling motion of the impeller. Appling the Bernoulli equation to swirling flow in the clearance in a relative coordinate fixed on the whirling motion, the pressure disturbance which generated the rotordynamic fluid force could be reasonably explained.