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Show 2.0 DESCRIPTION OF MODEL 2.1 GENERAL FRAMEWORK AND SOLUTION METHODOLOGY The numerical methodology and maj ority of the associated physical models incorporated in the coal combustion model used to predict the complex aerothermochemical features of the toroidal vortex combustor, Figure (1), derive from the original work at Imperial College and Sheffield university(3 ,4,5). The model seeks the solution of the governing di fferential transport equations, together with appropriate models for turbulence, combustion and radiation, i.e., k-c model describes the spatial evolution of the turbulence field, while a version of the six flux radiation model is used to compute the local radiation contribution to the stagnation enthalpy transport. Coal particle pyrolysis and char oxidation models (6,7) have been incorporated in the code to provide a complete description of the reacting flow field obtained in the slagging combustor. The numerical procedure employed to solve the above transport equations is an extension of the well-established SIMPLE algorithm(3). The procedure starts by reducing the differential transport equations to their respective finite difference forms by discretizing the entire calculation domain using a system of staggered grids and subsequently obtaining finite difference forms of the partial derivatives at each grid point . First order upwind differencing is used for the convective terms to ensure numerical stability and monotonic solution convergence at high Reynolds numbers, while diffusive influences are described via central differencing. |