Effects of Seal Geometry on Rotordynamic Fluid Forces. 1st Report. Experimental Results.

Abstract

This paper reports about experimental investigations of the rotordynamic fluid force on a centrifugal impeller with three types of wear-ring seals; i.e., a face seal and two types of toothed seals. The impeller is equipped with a vaneless diffuser. Rotordynamic fluid forces on the impeller in whirling motion were measured directly by using a 4-axis force sensor. Unsteady pressures were measured at several locations in the diffuser. It was found that, (1) At low flow rate, the fluid force and fluid force moment become maximum at a certain whirling speed caused by a coupling between the whirl and vaneless diffuser rotating stall. (2) The seal geometry affects the direction of the coupled fluid force relative to the direction of eccentricity through the change of unsteady leakage flow due to the whirl.