Abstract: In order to study the effects of transection transformation form on performance of serpentine 2-D exhaust system，three serpentine 2-D exhaust systems with different transection transformation forms which are A1 a rapid area change at the entrance and slow change at the exit，A2 a modest area change from the entrance to the exit，and A3 a rapid change at the exit and slow change at the entrance were built based on an axisymmetric exhaust system. These exhaust systems have the same length，centerline，inlet diameter，exit area and aspect ratio and all of them completely blocked the internal components such as turbine if viewed directly behind the exits. The effects of transection transformation form on thrust and infrared characteristics of three exhaust systems were studied numerically. The results show that，relative to the axisymmetric exhaust system，the thrust of A1，A2，A3 exhaust systems reduce by 3.8%，3.1% and 2.7%，respectively. The integral infrared radiation intensity of these three exhaust systems have similar spatial distribution，and the maximum deviation among them is within 13.8%. Compared with the axisymmetric exhaust system，the integral infrared radiation intensity of all three serpentine 2-D exhaust systems reduces at least 97% in the direction right behind the exit of the nozzle，and reduces at least 66.8%，30.2% and 34.1% in the direction vertical to the axis of the exit of the nozzle on the side，upper and lower detection planes respectively. In summary，the A3 serpentine 2-D nozzle has better performance considering both thrust and infrared characteristics.

Key words: Exhaust system；Serpentine 2-D nozzle；Infrared radiation；Transection transformation

摘要： 为了研究截面变化类型对双S形二元排气系统性能的影响，基于轴对称排气系统，建立了前急后缓(A1)、缓急相当(A2)、前缓后急(A3)三种过渡截面变化类型的双S形二元排气系统模型，这些模型具有相同的长度、中心线、进口直径、出口面积和宽高比，并且对发动机涡轮等部件完全遮挡。采用数值计算研究了截面变化类型对推力及红外特性的影响。研究结果表明:A3，A2，A1型双S形二元排气系统的推力依次降低，与基准轴对称排气系统相比，分别下降了2.7%，3.1%，3.8%；三种排气系统红外辐射强度的空间分布规律基本相似，幅值差异在13.8%之内；与基准轴对称排气系统相比，总体而言，不同截面变化类型的双S形二元排气系统在0°方向红外辐射强度均降低了97%以上，在侧向、上方和下方探测面的90°方向分别降低了66.8%，30.2%和34.1%以上。综合考虑推力及红外特性，前缓后急型过渡截面变化类型的双S形二元喷管是较优的选择。

关键词: 排气系统；双S弯二元喷管；红外辐射；过渡截面