发动机背负式安装无人机的排气系统红外特征的计算研究

用数值模拟的方法研究了对发动机背负式安装的无人机排气系统的红外辐射特征.排气系统的流场采用商业软件计算,红外辐射特征采用根据离散传递法自行发展的程序进行计算,研究了排气系统在3～5μm波段红外辐射强度的空间分布.在红外辐射计算过程中,考虑了喷管内壁的发射和反射、燃气组分CO₂、H₂O和CO的吸收-发射、后机身结构的遮挡以及大气吸收等影响.结果表明:通过发动机的背负式安装、尾喷口的下遮挡设计及其相对机身的内缩可使排气系统在下半球的红外辐射强度明显降低,但由此也造成了上半球的辐射强度有所增强;大气对该无人机排气系统前半球红外辐射的吸收明显强于后半球. 

Numerical simulation of infrared radiation characteristics for exhaust system of an UAV with engine installed on the back of the fuselage

Anumerical study was conducted on infrared radiation characteristics in the waveband of 3～5 μm for exhaust system of an unmanned aerial vehicle(UAV) with engine installed on the back of its fuselage.The flow field of the exhaust jet was calculated with commercial software FLUENT.The infrared radiation characteristics were calculated by using the software developed by the authors based on discrete transfer method.In the computation,multiple effects were considered,which included the emission and reflection of the nozzle wall,the absorption and emission of species of combustion gas,e.g.CO₂,H₂O and CO,the shelter of fuselage,and the absorption of atmosphere.The results show that by installing the engine on the back of the fuselage,sheltering the nozzle from its underside and forward shifting the nozzle exit relative to the aft-fuselage,the infrared radiation of the exhaust system to under hemisphere is reduced evidently,but on the other side the infrared radiation to the top hemisphere is increased;and the absorption effect of atmosphere on infrared radiation for the front hemisphere is stronger than that for the aft hemisphere.