Influence of diversified dihedral stator on the thermodynamic performance and flow loss characteristics of a variable core driven fan stage

The Variable Cycle Engines (VCE) have emerged as the unequivocal choice for the next generation of aircraft power systems, with the core driven fan stage (CDFS) playing a crucial role in determining its performance. In this study, the variations in performance improvements of CDFS with different dihedral stator schemes are analyzed, and a weight-adjustable comprehensive improvement coefficient is defined. The results indicate that under different modes, a dihedral angle of 10° provides optimal improvements in peak efficiency and maximum pressure rise, while the optimal dihedral angle for stability margin improvement varies depending on the operating mode. The influence of dihedral height on performance is relatively minimal compared to the dihedral angle. By integrating flow field analysis and quantitative loss analysis, it is observed that the dihedral blade can effectively mitigates the interaction between the trailing edge recirculation vortex and other vortex in the stator, resulting in a significant reduction in secondary flow losses and wake losses. However, under near stall conditions, excessively large dihedral schemes in the stator intensify the interaction between secondary flow vortices, leading to premature flow instability.