Currently, the design of advanced compressor blades has reached the full Three-Dimensional (3D) modeling stage. When analyzing the reasons for the failure of popular corner stall prediction criteria for axial compressors to predict the corner flow state in modern compressor 3D blades with end-bend and composite bend-sweep characteristics, it is believed that, in addition to the dihedral angle factor in the corner, the variation of the dihedral angle along the flow path is an important factor that has not been considered to date. In light of this, this study first uses the characteristic effects of the diffuser on the deceleration and pressure increase in airflow to design a series of physical models of varying dihedral angle diffusers that are equivalent to compressors. Based on these models, a quantization parameter is established to characterize the development speed of the intersection of boundary layers at the corner under varying dihedral angle and adverse pressure gradient conditions. After combining this with the effects of secondary flow, a Modified diffusion factor DJ (MDJ) is developed to describe the development of corner flow from the leading edge of the blade to its trailing edge under varying dihedral angle conditions. Finally, based on a compressor cascade database, an improved criterion for predicting corner stall in axial compressors using the MDJ diffusion factor is proposed. The validation results, based on extensive experimental data of compressor blades, reveal that this improved criterion can significantly enhance the accuracy of corner stall predictions in the 3D blades of modern compressors compared to currently used prediction criteria, by taking into account the effects of variations in the dihedral angle.

For hypersonic vehicles, certain issues are crucial to the success of flight plans, including sudden increase in surface heat flux, rising aerodynamic drag coefficients, and changes in intake airflow caused by boundary layer transition. Therefore, conducting in-depth research into boundary layer transition phenomena at hypersonic speeds is imperative. An improved k-ω-γ transition model is utilized to numerically simulate the transition characteristics of the Hypersonic Transition Research Vehicle (HyTRV). Firstly, the results of the baseline condition of the HyTRV obtained with the improved k-ω-γ transition model are compared with the results of wind tunnel test, affirming that the transition model possesses a good predictive capability for the transition phenomenon of the HyTRV configuration. Then, the transition properties of the HyTRV configuration are analyzed, disclosing the existence of streamwise vortex instability, secondary instability, and cross-flow instability on HyTRV to induce boundary layer transitions. Finally, different transition configurations of HyTRV at various angles of attack are investigated. As the angle of attack increases, the streamwise vortex on the windward surface becomes compressed, and the streamwise vortex on the leeward surface moves upward. The deformation and movement of the streamwise vortex lead to changes in the transition configurations, which results in the merging of different transition areas. This research not only reveals the pattern of changes in the HyTRV's shape with varying angles of attack, but also demonstrates the significant application potential of the improved k-ω-γ transition model in addressing complex shapes of hypersonic vehicles. It offers an effective analytical tool for in-depth exploration of boundary layer phenomena in complex vehicles.

It has been recently shown that Sub Boundary layer Vortex Generator (SBVG, abbreviated as VG hereafter) can suppress the Cross-Flow (CF), and therefore, can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages. However, when VGs are applied in high-load compressors, it is difficult to achieve ideal results. This is because the definition of the VG attack angle in the presence of CF in existing research is confusing, and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle. Therefore, this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate. The differences in the flow phenomena around a VG both with and without CF are also studied. The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect. However, the cross velocity increases when surmounting the primary vortex induced by the VG, except that this enhanced CF is less conspicuous for larger VG heights. Compared to the cases without CF, the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF.