Abstract
In a turbomachinery operated at the supercritical speed, a self-excited vibration can cause serious damages to both rotor and stator parts of the machine. The forces resulting from such vibrations are commonly called "rotordynamic fluid forces". The present paper reports about the rotordynamic fluid forces on an open-type centrifugal impeller. By generating an eccentricity, rotordynamic fluid forces were measured on an open-type centrifugal impeller with the type number of 0.33 in the cases with one vaneless and two vaned diffusers under the whirling motion. It was found that there is a destabilizing region near the whirl speed ratio ω/Ω =1 at design and lower flow rate in addition to a destabilizing region at small positive whirl ratios.
