Stability assessment is one of the important subjects in airworthiness certification. Many destabilizing factors can deteriorate the performance and stability margin of the compressor, and there are coupling effects between the external factors. This paper applies a computational method to investigate the coupling effects of total pressure distortion and low Reynolds number on an axial transonic compressor. The study was carried out on NASA stage 67, in which extensive open experimental data is available. Full annulus, steady, three-dimensional CFD has been used to study the coupling effects of 180-deg inlet distortion at low Reynolds number. The assessment of the stability margin loss under coupling effects by traditional methods results in a relative error of 27%. The local operating point of the rotor at different passages has been tracked, and the results reveal the reasons for the failure of model predictions. Combined with the analysis of the flow field under coupling effects, development solutions for the traditional model are proposed. The modifications to the model agree well with the calculation results. Finally, the improved model was validated. And according to the analysis of the rotor passage working points, the rationality of the model modification was verified.

The performance and stability of the transonic fan stage with a nonuniform inflow is a key issue in aero engine operation, and the coupling of inlet distortion and low Reynolds numbers at high altitude creates more severe challenges to aero engines. This work used computational methods to explore the performance and stability of a transonic fan stage with inlet distortion and a low Reynolds number. To investigate this issue, the transonic fan stage NASA stage 67 with a 180° total pressure distortion at a low Reynolds number was selected as the test case. Full-annulus 3D unsteady simulations were conducted to reveal the details of the flow field under coupling conditions. The computational results under different conditions were analyzed and showed that the coupling effect was not linearly stacked with single factors. The low Reynolds number in the coupling case thickened the boundary layer on the blade surface, and, on the one hand, the profile loss in the hub region increased. On the other hand, the structure of shock wave was converted in the tip region, which increased the shock loss significantly. In addition, the variation in the shock wave structure reconstructed the pressure distribution on the blade surface, allowing the fluid to migrate to the tip region, which affected the tip flow structure and ultimately delayed the stability boundary.

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