Investigation of model development for deterministic correlations associated with impeller-diffuser interactions in centrifugal compressors

Abstract

The average-passage equation system (APES) provides a rigorous framework to account for the deterministic unsteady effects by the so-called deterministic correlations (DC), which include both deterministic stress correlations (DCS) and deterministic total enthalpy correlations (DCH). These correlations should be modeled to close the system of equations. In this paper, the distribution of DC in a transonic centrifugal compressor is presented, and its relative importance is revealed. The assumption made by Adamczyk that the pure unsteady fluctuation is significantly smaller than the spatial fluctuation is verified at the impeller-diffuser interface. The decomposition of DCH is also discussed to determine its two different physical mechanisms. Finally, the transport equations in terms of DCS in cylindrical coordinates are derived, and the terms are evaluated to determine the ones that are necessary to model. All these analyses significantly contribute to our model development for DC in centrifugal compressors.