Numerical Study on Radiant Efficiency of a Porous Burner Under Different Conditions

摘要

The present study deals with investigating the effects of different parameters on the radiant efficiency of three-dimensional rectangular porous radiant burners. In the present work, combustion phenomenon and heat transfer characteristics in the porous radiant burner are numerically studied. Methane-air mixture flows through the burner as the reactant. A multistep methane-air combustion with detailed kinetic mechanism was used to calculate heat released during combustion process. Nonlocal thermal equilibrium between gas and solid phases is accounted for, and two separate energy equations are considered for these phases. Moreover, the discrete ordinate method is employed to find the radiative term in the solid energy equation, whereas radiation effects are neglected in the gas phase compared to the solid phase, and so the gas phase is considered to be transparent to thermal radiation. The governing equations, including energy equations for the gas and solid phases, the radiative transfer equation, and the species conservation equation, are numerically and simultaneously solved to find the thermal characteristics of porous radiant burners. By solving the governing equations, temperature fields, species concentrations, and radiative heat flux distributions through the porous burner are found. Then, the effects of different important parameters, such as optical thickness, scattering albedo, excess air ratio, and porosity on the radiant efficiency of the burner, are evaluated.