A Parametric Numerical Study of the Effects of Inlet Swirl Distortion on a Transonic Compressor Stage

Abstract

The ingestion or manifestation of a vortical flow can have dramatic effects on an aero engine. It is therefore imperative to quantify these effects and understand their underlying mechanism. This numerical study analyses the response of a transonic compressor stage to the ingestion of different streamwise vortical distortions using steady-state CFD. The vortex is described using a number of features, which are varied and combined together in order to generate a wide range of different swirl disturbances. The initial aim of this research is to identify the vortex features which have the highest impact on compressor performance. A numerical model of a compressor stage is generated which enables prescribed vortical flows to be imposed at the domain inlet. The method is validated against experimental data which was obtained under clean, undistorted conditions. The response of the compressor following the ingestion of a vortex is assessed both in terms of overall compressor performance parameters as well as more detailed aerodynamic characteristics. The results show that the compressor is sensitive to the vortex magnitude, core size, polarity and radial location. Furthermore, co-rotating, high-strength vortices which are ingested in the near-hub region cause the most significant drop in pressure ratio and corrected mass flow. In contrast, counter-rotating vortices cause little change in compressor performance. Overall, the work shows that modest swirl distortions can have a notable impact on the compressor performance and stability, and highlights the growing need to develop methods and an understanding of how this class of distortion can be evaluated during the engine design phase.