Effect of Particle Size Distribution and Complex Refraction Index of Alumina on Infrared Rocket Plume Signatures

Abstract

ABSTRACT Although there are several studies existing in the literature modeling the infrared radiation signatures of solid motor rocket plumes, none of them investigate the effect of some simplifying assumptions such as using gray optical properties, Sauter-mean/mass-mean diameters, temperature-independent optical properties, etc., on thermal radiation characteristics of rocket plumes. These assumptions have the potential to improve the computational efficiency of the radiative transfer calculations by reducing the CPU time required by the solution of Mie theory. Therefore, the objective of this study is to investigate the influence of using (i) mean diameters instead of a particle size distribution (PSD), (ii) optical properties for different phases and crystal structures of Al2O3, (iii) temperature-independent optical properties of Al2O3, and (iv) gray optical properties of Al2O3 particles instead of spectral ones on the radiative heat transfer predictions under rocket plume conditions. For this purpose, a 3-D radiation model based on discrete ordinates method (DOM) coupled with statistical narrow band correlated-k (SNBCK) and Mie theory is utilized. Based on the outcomes of this study, it can be concluded that utilizing mean diameters, temperature-independent optical properties, and gray optical properties of Al2O3 for the calculation of particle radiative properties provides reasonably accurate radiative heat transfer predictions. Moreover, presence of different phases and crystal structures of Al2O3 in the rocket plume leads to significantly different infrared radiation signatures.