A Hybrid Approach for the Modelling of Axial Compressor Surge

Abstract

This paper discusses the results of a hybrid approach, which couples the Moore–Greitzer potential flow model and the Navier–Stokes solution to predict the viscous effects on the axial compressor surge. The viscous effects are accounted by the inclusion of a duct between the compressor exit and the plenum inlet. The unsteady mass flow solution from the Moore–Greitzer model is supplied as an inlet boundary condition, to the duct, to solve the Navier–Stokes equation. The viscosity is seen to damp the surge oscillations and alter the character of oscillations significantly. A shortcoming of the Moore–Greitzer model in predicting proper phase relationship between the compressor flow and the plenum pressure is pointed out and the proposed hybrid approach is shown to overcome this flaw to a greater extent. It is depicted that this hybrid approach captures the existence of rotating stall disturbances in the combustor, during a typical classic surge cycle, as reported in the literatures. Thus this hybrid model is more physically appropriate in describing the plenum pressure oscillations than the Moore–Greitzer model. The combustor pressure oscillations from the hybrid approach shows two distinct time scales that can influence the combustor efficiency.