Effect of Emissivity and Reflectance on Infrared Radiation Signature of Turbofan Engine

Abstract

Directional emissivity model and bidirectional reflectance distribution function model of typical metal surfaces are established for improving the prediction of the midwave infrared signature of a turbofan engine exhaust system. The reverse Monte Carlo method is applied to calculate the infrared signature of the engine exhaust system. The results show that the infrared radiation signature of turbofan engine exhaust system is greatly affected by the emissivity and bidirectional reflectance distribution function of the wall surfaces of the exhaust cavity. In the rear detection direction of the engine, the difference of the infrared signature between exhaust cavity with high emissivity and the exhaust cavity with low emissivity is about 26%. By reducing the emissivity of high-temperature components, increasing the emissivity of low-temperature components, and controlling the wall specular reflection, the infrared signature in the rear direction of the engine could be greatly reduced, for example, up to 40% for the case studied in the present work.