Using computational fluid dynamics ( CFD) method, we performed numerical simulations on the wind tunnel test model of conformal inlet and expansion nozzle;they were aimed at verifying the reliability of the bounda⁃ry conditions on power simulation. Keeping in mind the stealth and conformal requirements of twin⁃engine flying wing UAV, we designed a S⁃shaped inlet with rectangular intake and a circular⁃rectangle nozzle. And then numeri⁃cal simulation was carried out on the intake and exhaust system, and it was also applied to studying the aerodynam⁃ic performance of UAV and three⁃dimensional flow field characteristics of the intake and exhaust. Results and their analysis indicate:(1)the lift/drag characteristic of flying wing UAV declines when adopting the intake and exhaust, but it can be used to improve the longitudinal moment characteristic under the low Mach number 0.5 and 0.6;(2) with increasing Mach number, the total pressure recovery coefficient decreases and the distortion coefficient increa⁃ses, while the axial thrust coefficient increases and the thrust performance remains relatively satisfactory; the inlet performance decreases rapidly at the high Mach number 0.7;so we should pay more attention to the right border of the flight envelope in the design;(3)the sideslip angle exerts greater influence on the inlet performance, while the thrust performance of nozzle is less affected;so we also should pay more attention to the impact of sideslip angle on inlet.%利用计算流体力学（ CFD）方法，分别针对保形进气道和膨胀尾喷管风洞试验模型进行数值模拟，验证了模拟进排气动力边界条件的可靠性。再基于飞翼布局无人机双发动机布局下隐身与保形设计要求，设计了矩形进气口S弯进气道和圆矩形喷口尾喷管，并利用数值模拟方法对无人机进排气系统进行了计算分析，获得了无人机全机气动性能及进排气三维流场特性。研究表明：①进排气使得飞翼无人机升阻特性有所下降，但低马赫数（0．5，0．6）下能改善无人机俯仰力矩特性；②随着马赫数增加，进气道总压恢复系数减小且畸变指数增加，而尾喷管轴向推力系数则升高，且推力性能保持较好；高马赫数（0．7）下进气道特性下降较快，设计时应多考虑飞行包线右边界；③侧滑角对于进气道性能影响较大，而尾喷管推力性能受侧滑角影响较小，设计时应多考虑进气道侧滑影响。
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