Three dimensional numerical simulation of combustion and heat transfer in porous radiant burners

In the present study, combustion phenomenon and heat transfer in a three-dimensional rectangular porous radiant burner are numerically studied. Methane-air mixture with five-step reaction mechanism is used to model the combustion process inside the porous matrix. Because of the non-local thermal equilibrium between solid and gas phases, separate energy equations for each of them are numerically solved. Besides, the discrete ordinates method is used to solve the radiative transfer equation for solid phase, where the gas phase is considered to be transparent. The set of governing equations including, gas and porous energy equations, the chemical species transport equations and the radiative transfer equation are simultaneously solved to calculate temperature profiles, radiative heat fluxes and species concentrations inside the porous medium. By this technique, thermal characteristics of porous radiant burners operating under different steady conditions are carried out. Results show that by increasing the excess air ratio, porous burner operates under low maximum temperature and consequently less emission of pollutants in the combustion product. Also, numerical results reveal that thermal behavior of porous burner is much affected by the optical thickness of radiating medium. Good agreement is found between numerical results and theoretical data obtained by other investigators.