Shock Induced Vortices in Transonic Compressors: Physical Interpretations

Abstract

Unsteady aerodynamics is becoming more and more important for future compressor improvements. It has to be taken into account to reduce the amount of uncertainties for increasing the performance. Uncertainties regarding unsteady blade row interaction are difficult to approximate due to the complex flow phenomena and the high computational effort to evaluate these phenomena. The optimal axial gapping for transonic compressors is particularly difficult to define. A wide range of axial gappings for two different state of the art compressor front stages (F-class and DLR Rig250) have been simulated to understand the underlying physics and to derive design rules for the optimal axial gapping. The incidence angle reduction due to shock induced vortices has not jet been fully investigated. Predicting the exact vortex trajectory in the rotor passage would be a critical step in assessing this reduction in incidence angle. A function to predict the deviation compared to the steady state compressor performance is usefull for future design processes.