2D exhaust nozzle with multiple composite layers for IR signature suppression

Abstract

The IR (Infrared) signature generated from hot sections of the aircraft increases potential to be traced by IR detection system and severely reduces aircraft survivability during the mission. Main sources of IR signature are high temperature parts of the aircraft and the engine such as exhaust nozzle, jet pipe, rear-fuselage, and exhaust gas plume above 400 °C, and they generate detectable 3 to 5 um wavelength IR signature. The novel 2D engine exhaust nozzle with multiple composite layers is proposed to suppress high temperature IR signature from behind, in this study. The 2D exhaust nozzle with ellipse-shaped cross-sections with high aspect ratios can disperse high temperature core gas flow, and can enhance mixing performance with bypass air flow. Thus, this reduces the exhaust gas plume temperature and masks the engine hot sections from behind. In order to suppress high temperature IR signature from the nozzle surface, this study constructs a ceramic insulator between the outermost surface layer and the innermost surface layer. The innermost surface layer is constituted by C-SiC (carbon fiber reinforced silicon carbide composite) with excellent erosion performance for high speed and high temperature gas above 1400 °C, and the outermost layer is formed of CFRP (Carbon Fiber Reinforced Plastic) that can maintain structural strength even with the axial thrust and inner pressure. In this study, the 2D-shape C-SiC nozzle was fabricated through melting Si infiltration process, and the nozzle was completed by stacking ceramic insulator and CFRP above it. The engine application test confirmed that the outermost temperature of the proposed exhaust nozzle was kept below 100 °C, and the IR signature was also reduced by 20% compared to the coaxial exhaust nozzle. The 2D exhaust nozzle proposed in this study can be applied to aircraft that requires stealth capability through structural optimization in the future works.