Toward high-efficiency design for jet-based flow control in high-pressure turbine vanes

Variable geometry turbines offer significant efficiency benefits under off‑design conditions, but conventional adjustable guide vanes face severe challenges in harsh high‑pressure turbine environments. Jet-based flow control (JFC), which operates without moving parts, offers a promising alternative. This study employs numerical simulations to investigate the effects of aerodynamic and geometric parameters on JFC performance, evaluating net benefit and economic feasibility based on outlet mass flow and regulation efficiency. The results show that JFC introduces complex flow structures, nearly doubling the total losses compared to the baseline. The choked primary flow induces a regulation saturation effect, stabilizing outlet flow variation and ensuring operational robustness in real turbine conditions. Increasing the jet pressure ratio expands the regulation range but does not improve efficiency, which remains around 0.55 under the baseline geometry. Consequently, geometric optimization is critical. Counterflow jetting at 60° significantly enhances efficiency by strengthening the upstream flow structure, increasing the average regulation efficiency to 1.06. The optimal jet position is not fixed but varies with jet pressure ratio ( JPR ). At low JPR, jetting at the throat position maintains high efficiency. And at high JPR , the jet position shifts upstream to address the downstream shift of the jet peak penetration point, thus maximizing the regulation range. Wider slots reduce regulation efficiency due to increased jet contribution to the outlet flow, thus the smallest feasible slot width is recommended. In addition, slot‑internal losses are found to rise with JPR and counterflow angle, especially under high‑pressure‑ratio conditions. Based on the above findings, this study not only clarifies the fundamental mechanisms governing JFC performance in high-pressure turbines but also establishes the design-priority for achieving high-efficiency flow control.