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Show -3- O axisymmetric geometries, with or without swirl, are permitted. Arbitrary numbers of species and chemical reactions (kinetic and equilibrium) are allowed. A sub-grid scale turbulence model, which is described in Reference 2, is included in the version of the code used in this study. The major changes that were required for the coal gasification study were the conversion of the evaporating liquid droplet model to a devolatilizing solid-particle model, the inclusion of radiative heat transfer, and the modification of the chemistry submodel for application to coal chemistry. In addition, the code was extensively tested against single-phase and multiphase experimental data to determine its accuracy when applied to problems and at scales different from that of the engine-cylinder study. These tests led to several modifications of the code that have improved its robustness and ease of application. A thorough description of these modifications and additions is given in Reference 3. In this paper we describe only the most significant aspects of the new modeling, some of which provide improvements over the procedures described in Reference 1. These improvements are described in the next section. We also present results of the application of the code to a study of entrained coal gasification. II. PHYSICAL MODELING A. Radiative Heat Transfer The radiative heat transfer model used in this study is a modification of a nonequilibrium radiation model described by Alrae, Westmoreland, and Fry [4]. In this procedure the transport equation for the radiation energy density a_ . 3(rF ) 8F . 3E 1 r z c / _4 _\ C s -.4 _\ /,x -r- + = + -=- - -r- • (aT - E) + - (aT - E) (1) 3t r 3r 3z A g A p g P is solved together with the gas and particle energy density equations, 3(pl) , & = --T- U T * - E) + S (2) at A g g and 3(pc T) . P P = - f - (aT4 - E) • S . (3) dt A p p P Here c is the speed of light, X is a mean free path for photons, a is the radiation constant, T is temperature, S denotes other contributions to these equations that are not considered here, p is density, I is specific internal energy, c is specific heat, and the subscripts g and p denote gas and particle, respectively. |