Investigation on influence mechanism of wall coating on infrared radiation signature of serpentine nozzle

Stealth performance is one of the most important factors to evaluate the technical level of modern battleplane. Serpentine nozzle can block the direct radiation transmission path between the high-temperature components in exhaust system and the infrared detector, thus suppressing the infrared radiation signature. However, due to the reflection characteristics of nozzle wall, this method can also cause indirect transmission of infrared radiation through the wall reflection to form a local high radiation area. Motivated by previous researches on the application of serpentine nozzle wall coating in electromagnetic radiation suppression. Wall coating is applied to serpentine nozzle to suppress infrared radiation intensity in this paper. Aiming at the situation of turbofan engine using serpentine nozzle, the influence mechanism of coating position, area and emissivity of serpentine nozzle on infrared radiation signature is calculated and analyzed, and the scheme of wall coating which has the least coating area and can effectively suppress infrared radiation transmission is also studied. The results show that reducing wall coating emissivity will strengthen the indirect transmission of infrared radiation, then cause the increase of exhaust system infrared radiation intensity, while increasing wall coating emissivity will reduce wall coating reflectivity, and the local high radiation area caused by indirect radiation transmission can be effectively prevented. The research also found that the infrared radiation signature of exhaust system can be effected only when the emissivity adjustment of serpentine nozzle wall which can be detected directly by infrared detector. After adopting the optimized wall emissivity coating scheme, the infrared radiation intensity of serpentine nozzle for turbofan can be reduced by 51.3% on the original basis while the coating area only accounts for 25.1% of the nozzle area.