Infrared stealth is an essential feature for enhanced survivability of aircraft on a modern battlefield. To counter target detection and search and tracking system of the enemy, the infrared signature is reduced by various methods. They include deforming the aircraft shape, spraying particles around nozzle exit, or applying radiation painting to the surface. The infrared signature is significantly affected by propulsive sources including the engine/nozzle, exhaust gas, and heating due to exhaust gas. Accordingly, reducing the infrared signature of the aircraft propulsion system is the most important factor in improving the infrared signature stealth performance of the aircraft.
In this study, as a countermeasure to infrared tracking seekers, a serpentine nozzle was designed based on several design variables to reduce the plume infrared signature generated from high temperature exhaust plume. A commercial software ANSYS FLUENT was used to analyze the effects of design variables and flight conditions on the infrared stealth performance. The flow characteristics for various design variables which are aspect ratio, shield ratio, and centerline ratio were analyzed by comparing contour plots, core plume length defined by a temperature level, and thrust performance. Finally, the total radiance and intensity of the plume infrared signature were calculated based on the narrow-band model at various view angles according to the IR requirements of military aircraft.
As a result, it was confirmed that when the double serpentine nozzle was applied, there was an effect of reducing the IR signature. In addition, the flow characteristics inside the nozzle according to each design variable were analyzed, and the IR signature trend according to the elevation angle and azimuth angle were identified.