Towards a multi-physics numerical strategy dedicated to the prediction of rotor/stator interactions within modern turbomachines

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The evolution of environmental regulations for the reduction of CO2 emissions combined with a tough economic context are key factors for understanding recent design evolutions of aircraft engines. In a very competitive market, engine manufacturers must develop more efficient engines and two strategies are usually considered: (1) the use of lighter materials and (2) the reduction of clearances between rotating and static components. As a counterpart of an improved efficiency, the reduction of clearances yields more frequent structural contacts between the engine components which may initiate hazardous interaction phenomena. The ability to predict and mitigate these interactions has thus become imperative for engine manufacturers. The very high cost of full-scale experimental set-ups for analyzing such interactions motivates the development of dedicated predictive numerical methods. However, the complexity of the physical phenomena at play makes it impossible to use commercial softwares. In this context, the proposed research project aims at developing a multi-physics approach for the simulation of rotor/stator interactions, with the ability to predict interaction phenomena at the engine scale. It focuses on a few topics for which decisive breakthrough may be achieved. First of all, the realistic modeling of full engine components such as a compressor and a turbine featuring their manufacturing imperfections and including potential contact interfaces is a prerequisite for carrying out efficient numerical simulations. Second, it is proposed to simulate rotor/stator interactions accounting for thermal and aerodynamic effects. In fact, while significant temperature increase has been witnessed on experimental set-ups, the coupled analysis of structural interaction phenomena with thermal effects is yet to be done. Finally, it is proposed to establish design guidelines in order to create bladed components robust with respect to interactions stemming from structural contacts. Current design guidelines commonly used in the industry rely on empirical linear considerations that fail to predict non-linear interactions. The definition of new criteria related to the component vibratory response to structural contacts is thus a fundamental issue and goes way beyond the scope of the aerospace industry. Taken all together, the proposed research project aims at gaining a fundamental understanding of interaction phenomena that are potentially destructive for an aircraft engine, in order to ensure a safe flight for passengers while reducing their environmental impact.