Convoluted aero-engine intakes are often required to enable closer integration between engine and airframe. Although the majority of previous research focused on the distortion of S-duct intakes with undistorted inlet conditions, there is a need to investigate the impact of more challenging inlet conditions at which the intake duct is expected to operate. The impact of inlet vortices and total pressure profiles on the inherent unsteady flow distortion of an S-duct intake was assessed with stereo particle image velocimetry. Inlet vortices disrupted the characteristic flow switching mode but had a modest impact on the peak levels and unsteady fluctuations. Non-uniform inlet total pressure profiles increased the peak swirl intensity and its unsteadiness. The frequency of swirl angle fluctuations was sensitive to the azimuthal orientation of the non-uniform total pressure distribution. The modelling of peak distortion with the extreme value theory revealed that although for some inlet configurations the measured peak swirl intensity was similar, the growth rate of the peak values beyond the experimental observations was substantially different and it was related with the measured flow unsteadiness. This highlights the need of unsteady swirl distortion measurements and the use of statistical models to assess the time-invariant peak distortion levels. Overall, the work shows it is vital to include the effect of the inlet flow conditions as it substantially alters the characteristics of the complex intake flow distortion.

通常需要曲折的航空发动机进气口来实现发动机和机身之间的更紧密集成。尽管以前的大多数研究都集中在进气管未变形的 S 形管道进气口的变形上，但仍需要研究预计进气管运行的更具挑战性的进气口条件的影响。使用立体粒子图像测速法评估了入口涡流和总压力分布对 S 形管道入口固有的非定常流动失真的影响。入口涡流破坏了特征流动切换模式，但对峰值水平和不稳定波动的影响不大。不均匀的入口总压力分布增加了峰值涡流强度及其不稳定性。涡流角波动的频率对非均匀总压力分布的方位角方向敏感。用极值理论对峰值畸变进行建模表明，尽管对于某些入口配置，测得的峰值涡流强度相似，但超出实验观测值的峰值增长速度存在显着差异，并且与测得的流动不稳定性有关。这突出了非定常涡流失真测量的需要和使用统计模型来评估时不变的峰值失真水平。总体而言，这项工作表明，将进气流条件的影响包括在内是至关重要的，因为它大大改变了复杂进气流畸变的特征。用极值理论对峰值畸变进行建模表明，尽管对于某些入口配置，测得的峰值涡流强度相似，但超出实验观测值的峰值增长速度存在显着差异，并且与测得的流动不稳定性有关。这突出了非定常涡流失真测量的需要和使用统计模型来评估时不变的峰值失真水平。总体而言，这项工作表明，将进气流条件的影响包括在内是至关重要的，因为它大大改变了复杂进气流畸变的特征。用极值理论对峰值畸变进行建模表明，尽管对于某些入口配置，测得的峰值涡流强度相似，但超出实验观测值的峰值增长速度存在显着差异，并且与测得的流动不稳定性有关。这突出了非定常涡流失真测量的需要和使用统计模型来评估时不变的峰值失真水平。总体而言，这项工作表明，将进气流条件的影响包括在内是至关重要的，因为它大大改变了复杂进气流畸变的特征。超出实验观测值的峰值增长速度存在显着差异，与实测流量不稳定性有关。这突出了非定常涡流失真测量的需要和使用统计模型来评估时不变的峰值失真水平。总体而言，这项工作表明，将进气流条件的影响包括在内是至关重要的，因为它大大改变了复杂进气流畸变的特征。超出实验观测值的峰值增长速度存在显着差异，与实测流量不稳定性有关。这突出了非定常涡流失真测量的需要和使用统计模型来评估时不变的峰值失真水平。总体而言，这项工作表明，将进气流条件的影响包括在内是至关重要的，因为它大大改变了复杂进气流畸变的特征。