外并联型进气道模态转换过程中低速通道再起动特性OA

This paper investigates the unsteady flow characteristics within the inlet during the ram-to-turbo transition of a Turbine-Based Combined Cycle(TBCC)engine.Through a combined approach of wind tunnel test and Computa-tional Fluid Dynamics(CFD)simulations,it analyzes the evolution of the inlet shock system and the static pressure variation patterns along critical flow path locations,and acquires the dynamic restart characteristics of the low-speed duct during inlet mode transition and the influence of flow splitter rotational speed on this process.The results indicate that during the progressive opening of the low-speed duct under turbine-mode startup conditions,six distinct phases occur:in phase 1,flow splitter deployment initiates boundary layer ingestion into the duct,causing minor static pres-sure drop;in phase 2,supersonic core flow enters the duct,triggering significant static pressure rise;in phase 3,flow accumulation induces pressure buildup and shock train forward propagation,followed by shock traversal past the bleed cavity,with subsequent cavity depressurization causing shock recession;in phase 4,cyclic expansion/contrac-tion of the low-speed duct separation bubble induces shock oscillation;in phase 5,shock expulsion along the separa-tion bubble triggers inlet buzz;in phase 6,reduction in downstream Throttling Ratio(TR)terminates buzz,enabling low-speed duct restart.During the low-speed duct restart process,the rotational speed of the flow splitter vanes influ-ences both the frequency and amplitude of pressure oscillations within the flow path,with lower rotational speeds re-sulting in reduced oscillation frequencies and increased amplitudes.Moreover,during low-speed duct restart,the rota-tional speed also affects the onset timing of buzz,where lower speeds more readily trigger inlet buzz in the low-speed duct.This study provides a theoretical foundation for achieving smooth mode transition in combined-cycle engines.