EFFECT OF GASEOUS RADIATION HEAT TRANSFER ON NON-PREMIXED COMBUSTION OF AMMONIA IN POROUS MEDIA

This paper presents a Computational Fluid Dynamics (CFD) / Numerical Heat Transfer investigation on the effects of gaseous radiation heat transfer on non-premixed combustion of ammonia in porous media. The numerical radiation heat transfer is governed by the Radiative Transport Equation (RTE). The non-gray RTE is a multi-dimensional integro-differential equation (3 spatial dimensions, 2 angular dimensions, and 1 for the wavelength). Combustion gases require repeated solution of the RTE due to presence of the spectral absorption coefficient. Numerical simulation of the RTE in a medium comprised of combustion gases are found to be computationally intensive. Herein ANSYS FLUENT solved the RTE using the Discrete Ordinate (DO) method. The DO method uses a discrete number of beam directions incident on a particular cell in the CFD mesh. The coupling of the solution of the RTE via the DO method and Energy Equation occurs at the boundaries of the domain. Since the radiation coupling is weak, in order to improve computational overhead, the DO solution of the scalar equation from the RTE occurs every ten iterations of that of the flow equation iteration. The Weighted Sum of Grey Gas (WSGG) model is employed for the absorption coefficient calculations. The results herein show that correct modeling of gaseous radiation in reacting flows in porous media is paramount to capture the correct thermo-physics of the flame behavior. Results show that the inclusion of a porous media effects reduce the peak mole fraction of NOx by almost half in comparison to nonporous media flames.