Development and Validation of Standardized Infrared Radiation Model (SIRRM). Gas/Particle Radiative Transfer Model

Abstract : Analytical models have been developed to treat the coupled gas/ particle radiative transfer in exhaust plumes, monochromatically and in a band model approach. In addition, the availability of the particle optical parameters has been investigated. The requirements for the plume scattering model in SIRRM are: Coupled emission, absorption and scattering treatment; Multiple scattering with cylindrical geometry; Three-dimensional, non-uniform, axisymmetric medium; Arbitrary particle mixtures and size distribution; Line-by-line and band-model treatments; and Alternate levels of engineering approximation. These requirements are met by developing two basic approaches, a 6-flux and a N-flux approach. This distinction refers to the associated subdivision in angular space, six-orthogonal coordinates versus N nonorthogonal coordinates in azimuth and elevation, thus providing the alternatives of computational simplicity of the 6-flux model with generality of the N-flux model. Numerous parametric calculations were performed to study the effect of optical depth, scattering albedo, phase function and medium geometry on the target signature and computational requirements.