Inlet flow distortion is expected to play a major role in future aircraft architectures where complex air induction systems are required to couple the engine with the airframe. The highly unsteady distortions generated by such intake systems can be detrimental to engine performance and were previously linked with loss of engine stability and potentially catastrophic consequences. During aircraft design, inlet flow distortion is typically evaluated at the aerodynamic interface plane, which is defined as a cross-flow plane located at a specific upstream distance from the engine fan. Industrial testing currently puts more emphasis on steady state distortions despite the fact that, historically, unsteady distortions were acknowledged as equally important. This was partially due to the limitations of intrusive measurement methods to deliver unsteady data of high spatial resolution in combination with their high cost and complexity. However, as the development of aircraft with fuselage-integrated engine concepts progresses, the combination of different types of flow distortions is expected to have a strong impact on the engine’s stability margin. Therefore, the need for novel measurement methods able to meet the anticipated demand for more comprehensive flow information is now more critical than ever. In reviewing the capabilities of various non-intrusive methods for inlet distortion measurements, Filtered Rayleigh Scattering (FRS) is found to have the highest potential for synchronously characterising multiple types of inlet flow distortions, since the method has the proven ability to simultaneously measure velocity, static pressure and temperature fields in challenging experimental environments. The attributes of the FRS method are further analysed aiming to deliver a roadmap for its application on ground-based and in-flight measurement environments.

预计进气流变形将在未来的飞机结构中发挥重要作用，在这些结构中，需要复杂的进气系统将发动机与机身连接起来。这种进气系统产生的高度不稳定的变形可能对发动机性能有害，并且以前与发动机稳定性的损失和潜在的灾难性后果有关。在飞机设计期间，通常在空气动力学界面平面评估进气流变形，该界面被定义为位于发动机风扇特定上游距离处的横流平面。工业测试目前更加强调稳态失真，尽管在历史上，非稳态失真被认为同样重要。这部分是由于侵入式测量方法在提供高空间分辨率的不稳定数据方面的局限性，以及它们的高成本和复杂性。然而，随着具有机身集成发动机概念的飞机发展的进展，不同类型的流动畸变的组合预计将对发动机的稳定性裕度产生强烈影响。因此，对能够满足对更全面流量信息的预期需求的新型测量方法的需求现在比以往任何时候都更加重要。在回顾各种非侵入式方法对入口变形测量的能力时，发现滤波瑞利散射 (FRS) 在同步表征多种类型的入口流动变形方面具有最高潜力，因为该方法已被证明能够在具有挑战性的实验环境中同时测量速度、静压和温度场。进一步分析 FRS 方法的属性，旨在为其在地面和飞行测量环境中的应用提供路线图。