Turbulence Model Impact on Predicting Precursors to Surge Flow Instabilities in a Turbocharger Compressor

Turbocharger compressor simulations can improve the development of compressors with broad operating ranges and improved noise signatures. At low mass flow rates aerodynamic instabilities, known as rotating stall and surge, limit the operating range of the compressor. However, the triggering factors for these instabilities are currently unknown. High quality numerical methods are therefore needed to capture instabilities and to simulate reliable performance maps. The aim of this study is to improve the understanding of the chosen numerical approach going from design to off-design operating conditions. It is shown that flow structures are under-predicted using URANS k-ω SST and that a LES WALE method better captures the flow structures in the blade region. Further, the level of fluctuations in different parts of the compressor is presented. By increasing the predictive quality of the numerical simulations, the need for empirical calibration can be reduced and turbocharger matching can be improved.