A Blockage Model for Centrifugal Compressor Impellers

Abstract

This paper presents and discusses the results of an analysis in which the blockage distributions of four impellers were deduced from shroud static pressure measurements. The purpose of the analysis was to provide a means of estimating blockage for the jet-wake flow model for use in impeller design calculations. A parameter was investigated for correlating the blockage values against the combined effect of diffusion, curvature, and Coriolis acceleration. It was found that gross blockage accumulation correlates against this parameter with an uncertainty in blockage of ± six percentage points. Up to the point of the axial-radial bend of the flowpath, the analysis shows that blockage is controlled equally by diffusion, flowpath curvature, and the combined effect of blade curvature and Coriolis acceleration. In the radial portion of the impeller, further increase in blockage is controlled by Richardson number.