Ejector tip injection system for active aerodynamic compressor stabilization part II: CFD investigations

Injecting high-momentum jets of air into the rotor blade tip region of turbo compressors can increase its surge margin and even recover the compressor from unstable aerody-namic operation. The Institute of Jet Propulsion at the University of the German Federal Armed Forces Munich recently developed and patented a novel Ejector-based air Injec-tion System (EIS) for such active aerodynamic stabilization of the Larzac 04 jet engine low pressure compressor. This paper deals with detailed investigations of the aerodynamic conditions within the EIS by means of CFD simulations. First, several sensitivity studies concerning the mesh resolution respectively the boundary layer treatment and the neces-sity to apply a transition model are conducted. The CFD predictions of the final setup are validated utilizing experimental measurements of static wall pressure distributions and the air mass flow rates involved as outlined in the first part of this paper by Kern et al.(2017). This data is also used for detailed analyses of the flow conditions within the main aerodynamic components of the EIS.