Boron Slurry-fueled Jet Engine Exhaust Plume Infrared Signatures
Infrared radiation emitted from jet engine exhaust plumes plays a significant role in the detection of aircraft. Expected use of high-energy boron slurry fuels in advanced engines will produce gaseous and particulate B2O3 in their exhaust plumes. Infrared emission from B2O3 gas and the emission and scattering from the B2O3 particles must be included in the exhaust plume infrared signature calculations. This paper presents B2O3 particle scattering and emission properties (scattering cross sections, albedo, and scattering phase functions) generated from spectral radiative reflection and transmission data obtained from the literature. Kramers-Kronig analysis is used to convert the radiative data to index of refraction values. Radiation scattering parameters that are needed for the JANNAF Standardized Infrared Radiation Model code are generated from the index of refraction values using Mie scattering analysis for wavelengths from 2 to 25 µm. The Standardized Infrared Radiation Model is used to calculate the broadside infrared radiation emitted from isothermal and homogeneous models of turbojet and ramjet exhaust plumes. The calculations show that B2O3 influences the radiant emission and that the emission increases with increasing particle size and particle mass loading. The plume signature in spectral regions between the gas bands is very sensitive to the B2O3 particle size and concentration. Infrared signatures were also calculated using an isotropic scattering phase function. These signatures were up to 3% greater than the predicted signatures using the correct anisotropic phase function. © American Institute of Aeronautics and Astronautics, Inc., 1986, All rights reserved.