Non-axisymmetric endwall contouring for radial gap leakage control in variable stator vanes

Variable stator vanes (VSVs) serve as a critical aerodynamic control mechanism to optimize stage matching in multi-stage axial compressors. However, due to mechanical rotation constraints, complex flow structures such as gap leakage significantly reduce the compressor efficiency and stability margin. In this study, three-dimensional Computational Fluid Dynamics (CFD) simulations were carried out on the actual geometry configuration of VSVs in a specific fan to systematically evaluate the underlying flow physics and loss generation mechanisms. The numerical results indicate that the significant variations in the front radial gap during VSV adjustment are the primary cause of the performance deterioration. To prevent mechanical interference between the blade and the endwall, a substantial radial gap margin is required at certain adjustment angles. Consequently, the large-scale leakage flow strongly mixes with the mainstream and bypasses the penny, further intensifying low-energy fluid accumulation in the corner region. To mitigate these secondary flow losses, a non-axisymmetric endwall contouring control strategy is proposed in this paper. This design effectively accommodates variations in the front radial gap during rotation and spatially isolates the passage vortex from the gap leakage vortex, thereby significantly reducing corner losses. At the design incidence and adjustment position, this contouring scheme reduces the total pressure loss coefficient by 11.6% and the endwall loss by 28.7%. This approach provides an effective engineering strategy for improving the aerodynamic performance of variable stator configurations.