Numerical Study of the Effect of Multiple Tightly-Wound Vortices on a Transonic Fan Stage Performance

Abstract

As a result of the new engine design trends, the likelihood of tightly-wound vortices being ingested by the engine rises. Therefore, the risk associated with the ingestion of swirl distortion becomes a major concern. A numerical analysis of the response of a transonic fan stage to the ingestion of different distorted flow patterns is carried out using steady-state CFD. The CFD approach is generated and validated against experimental data for undistorted inlet conditions. Following the validation, a wide range of configurations with vortex flow distortions are analysed and evaluated. The change in global performance is quantified and the flow field is extensively analysed. Consequently, the parameters that have the most critical impact on the performance of the fan stage are identified. The study identifies a close relation between the number of vortices ingested and the change in rotor performance. However, the deviation from the clean rotor performance has been found to be independent of the circumferential distance between vortices. Additionally, the effects of the radial location, polarity and vortex magnitude have been assessed. Ingested co-rotating vortices cause a significant reduction in pressure ratio and corrected mass flow. In contrast, counter-rotating vortices are associated with an increase in the pressure ratio and corrected mass flow. The change in rotor performance increases with the strength. However, a dramatical drop in pressure ratio is observed for counter-rotating vortices when the vortex strength exceeds a critical value.