Numerical Investigation of Effect of Porosity and Fuel Inlet Velocity on Diffusion Filtration Combustion

Methane-air diffusion filtration combustion in a radiative round-jet burner was numerically investigated in this work. The purpose of this study was focused on the effects of porous media porosity and gas velocity on temperature distribution and CO and NO x emissions. Reduced chemical kinetics was used where air and methane were assumed to be at their stoichiometric ratio, while thermo-physical properties were varied per the solid matrix porosity variation. Combustion characteristics were evaluated based on conduction and radiation as the two primary heat transfer modes within the solid matrix. Numerical simulations were carried out based on a packed bed with 3 mm alumina pellets. Results show that combustion temperature increases while the temperature gradient decreases with the increase in porosity, yielding higher NO x , and lower CO emissions. Furthermore, the combustion temperature is the lowest and most uniformly distributed with 1 m/s and 3 m/s gas velocities, wherewith 3 m/s gas velocity, combustion occurs outside of the porous zone. The corresponding NO x and CO emissions are the lowest with 1 m/s gas velocity and increase with the increase in gas velocity from 1 m/s to 10 m/s.