Abstract: Base on CFD， the flow characteristics of over-under TBCC (Turbine Based Combined Cycle， TBCC) exhaust system was analyzed. A method to enhance the exhaust system performance by injecting high pressure secondary flow into the down wall of turbo-engine nozzle was proposed. And the effects of secondary injection on the performance， e.g， thrust coefficient and thrust vector angle were investigated in different flight Mach number. Results show that secondary injection produces bow shock， which can generate new flow separation region interaction with ramp of nozzle. Bow shock improve turbo-engine nozzle and ramjet nozzle pressure distributions， thus improve nozzle thrust and thrust vector performance， and obviously improve over-under TBCC nozzle performance at subsonic and transonic condition， which makes the axial thrust coefficient increase by 7.34% and thrust vector angle increase by 12.76°.

Key words: TBCC；Exhaust system；Secondary injection；Thrust coefficient；Thrust vector angle

摘要： 基于CFD数值模拟方法，分析了并联式涡轮基组合循环发动机(Turbine Based Combined Cycle，TBCC)排气系统的内外流场特性，提出了在涡轮喷管下壁面处喷入高压二次流以提升排气系统性能的方式，研究了不同飞行状态下二次流喷射对排气系统性能(推力系数、推力矢量角)的影响规律。计算结果表明:二次流喷射会产生弓形激波，与喷管上膨胀壁面附面层作用产生新的分离区，提升涡轮喷管和冲压喷管内的整体压力，从而改善并联式TBCC排气系统的推力及推力矢量性能，且对亚声速和跨声速飞行状态下的并联式TBCC排气系统性能改善比较明显，可使轴向推力系数最大提升7.34%，推力矢量角提升12.76°。

关键词: 涡轮基组合循环发动机；排气系统；二次流喷射；推力系数；推力矢量角