Vortex instability induced by blade-attached vortex generators in a supersonic compressor cascade under downstream throttling

Abstract

The unsteady flow related to shockwave/boundary layer interaction is one of the key factors leading to compressor instability, so it is important to develop an effective flow control method. In this study, based on three-dimensional numerical simulation, the control mechanism of blade-attached vortex generator (BVG) on shockwave oscillation in a typical C-type supersonic cascade is systematically investigated. The results show that the BVG induced vortices (VGV) can suppress 50.8% of the separation and significantly weaken the oscillation of the shockwave; therefore, the maximum pressure ratio increases by 7.8% and reduces the total pressure loss by 8.1% at the limit stall condition. The VGV shape is closely coupled with the direction of shockwave motion. When the shockwave moves upstream, bubble-type breakdown becomes evident; when it moves downstream, the breakdown develops into spiral type. Further research shows that BVG array spacing is the key to determining the control effect: the smaller spacing scheme (BVG 1, d = 2.5x) remains primarily synchronized with the main shockwave and maintains the spanwise symmetry, while the larger spacing scheme (BVG 2, d = 2.75x) introduces a local spanwise-asymmetric response within a single periodic BVG unit. Mode analysis further indicates that mode 1f represents the fundamental shockwave motion, mode 2f characterizes the local shockwave structure and passage shockwave, and mode 0.4fBVG 2 and mode 0.6fBVG 2 are associated with the spanwise-asymmetric VGV breakdown in 0.6–0.8Cax downstream of the shockwave. The results indicate that BVG spacing affects not only the separation suppression but also the dynamic stability of shockwave–VGV coupling.