Transonic flow characteristics in suction-surface adjustable vanes for adaptive cycle engines

Adaptive cycle engines (ACEs) represent a pivotal technology for future air transportation, with their development heavily dependent on advanced high-performance variable-geometry turbines. Conventional variable-incidence angle guide vanes incur efficiency loss and poor cooling due to tip leakage and restricted pivot on cooling flow. The suction surface adjustable guide vane was proposed to alleviate these issues, but its transonic flow physics—especially with clearance gaps—are not well understood. This study presents a high-fidelity large eddy simulation of an SSA guide vane with integrated coolant leakage gaps, analyzing flow characteristics, loss mechanisms, and performance at 0°, 5°, and 10° rotation under transonic conditions. Results show that leakage flow provides convective cooling while driving complex shock/vortex interactions. At 0°, leakage induces an oblique shock near the rear clearance alongside the passage normal shock. At 5°, suction surface rotation weakens the shock, reduces separation, and lowers wake entropy. At 10°, the shock system becomes a reflected pattern within the passage, dramatically altering the flow. The dominant loss mechanism arises from interaction between the end wall leakage vortex and the passage vortex. Loss increases nonlinearly with rotation, with the 10° case causing a disproportionately large rise in dissipation and total pressure loss. The vane reduces mass flow by 23% from 0° to 10°, while total pressure loss increases from 5% to 9.1%. This work provides key insights for designing next-generation variable-geometry turbines for ACEs.