Evolution of three-dimensional separation flows in the stator passages of an aggressive compressor transition duct

The increasing performance demands of modern aero engines necessitate the integrated design of compressor transition ducts with upstream components to reduce the axial length of the engine. However, this design approach narrows the spacing between the stator and the strut, making traditional research on transition ducts only with struts unsuitable. The numerical results and experimental oil flow visualization results were utilized to reconstruct the three-dimensional flow structures in the stator passages under various operating conditions. Additionally, numerical methods were employed to analyze the mechanisms of the strut’s effect on the upstream stator in an aggressive transition duct. The results show that the strut potential field increases the load on the upstream stator, leading to severe blade surface separation and corner separation/stall, and redistributes the inflow angle of the upstream stators circumferentially, resulting in significant differences in the flow structures within the stator passages on both sides. The separation flows within the stator passages mainly manifest in five types: pressure surface separation vortex, suction surface concentrated shedding vortex, suction surface separation vortex, suction surface-corner stall separation vortex, and suction surface separation vortex pair. Under different operating conditions, the separation flows within the stator passages are always composed of a part of these five types or a transitional state between two of them.