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

减少二氧化碳排放的环境法规的演变与严峻的经济环境相结合，是理解航空发动机近期设计演变的关键因素。在竞争激烈的市场中，发动机制造商必须开发更高效的发动机，通常考虑两种策略：(1)使用更轻的材料；(2)减少旋转部件和静态部件之间的间隙。作为提高效率的对应物，间隙的减少会产生发动机部件之间更频繁的结构接触，这可能会引发危险的相互作用现象。因此，预测和减轻这些相互作用的能力对发动机制造商来说变得至关重要。用于分析这种相互作用的全尺寸实验装置的非常高的成本促使了专用预测数值方法的发展。然而，物理现象的复杂性使得使用商业软件是不可能的。在此背景下，该研究项目旨在开发一种多物理场方法来模拟转子/定子相互作用，并能够预测发动机尺度上的相互作用现象。它侧重于可能取得决定性突破的几个主题。首先，对压气机和涡轮等具有制造缺陷并包含潜在接触界面的发动机全部件进行真实建模是进行有效数值模拟的先决条件。其次，提出了考虑热效应和气动效应的转子/定子相互作用的仿真方法。事实上，虽然在实验装置上观察到明显的温度升高，但结构相互作用现象与热效应的耦合分析尚未完成。最后，建议建立设计准则，以便创建关于结构接触产生的相互作用的叶片部件。当前行业中常用的设计指南依赖于经验线性考虑，无法预测非线性相互作用。因此，与结构接触的部件振动响应相关的新标准的定义是一个基本问题，远远超出了航空航天工业的范围。综上所述，拟议的研究项目旨在获得对飞机发动机潜在破坏性相互作用现象的基本理解，以确保乘客的安全飞行，同时减少对环境的影响。

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.