Abstract: With the development of both a simplified model for calculating the mode transition performance of the dual-flowpath combined inlet and the simulation model for high-Mach turbine engine under the windmilling condition，the dynamic performance simulation of full transition process from turbo mode to ram mode for a Mach 7 over-under Turbine-Based Combined-Cycle (TBCC) engine was conducted. Mode transition was divided into four typical sub-processes，including ramjet cool open，afterburner staged shutdown，turbine engine throttle down，and turbine engine cool down (windmilling close). A mode transition strategy was proposed based on the principle of smooth thrust variation. The simulation results show that: TBCC engine thrust transition mainly occurs in the sub-process from full augmentor to non-augmentor during mode transition; both the ramjet operating in the cool open condition and the turbine engine operating in the windmilling condition will deliver negative thrust，the maximum value of which will account for 5.3% and 13.7% of the total thrust after mode transition，respectively，during the early and later period of mode transition; when the turbine engine gets into the windmilling operation，mode transition work points are located at the low-speed and high-flow region of fan and compressor characteristics map，and the pressure ratio of fan and compressor varies to 1.0 along with the decrease of air mass flow，which is in good agreement with relevant experimental results.

Key words: Over-under；TBCC；Mode transition；Windmilling；Dynamic performance；Numerical simulation

摘要： 针对Ma7一级外并联式TBCC发动机，发展了组合进气道模态转换性能简化计算模型和高马赫数涡轮发动机风车性能计算模型，实现了TBCC发动机由涡轮模态至冲压模态完整转换过程的动态性能模拟。将模态转换过程划分为冲压发动机冷通流打开和涡轮发动机关闭加力、降转、风车关闭等四个典型阶段，基于推力连续准则提出了模态转换策略。计算结果表明:模态转换期间，TBCC发动机的推力转换主要发生在涡轮发动机由全加力状态变化至不加力状态过程中；模态转换前期处于冷通流状态的冲压发动机以及后期处于风车状态的涡轮发动机产生负推力，最大值分别为模态转换后总推力的5.3%和13.7%；当涡轮发动机进入风车状态时，风扇和压气机的工作点均位于其特性图的低转速大流量区域，此后随着涡轮发动机空气流量的减小，风扇压比和压气机压比均趋向于1.0，与相关试验结果基本一致。

关键词: 外并联式；TBCC；模态转换；风车；动态性能；数值模拟