Two-dimensional numerical study of combustion and pollutants formation in porous burners

Two-dimensional numerical predictions of temperature profiles and pollutants formation in a porous burner are presented and validated through their comparison with available experimental data. The burner under study integrates a heat exchanger where water is heated for household applications. The Navier-Stokes, the energy and the chemical species transport equations are solved and a multistep kinetics mechanism (77 reactions and 26 species) is employed. Thermal nonequilibrium is accounted for and the discrete ordinates method, for the case of isotropic scattering, is used. Centreline temperature predictions are in good agreement with the experimental results. Predicted CO and NO emissions are compared to experimental results for a 5 kW thermal power and several excess air ratios. The model underpredicts the CO emissions and overpredicts the NO emissions. This tendency is stronger for richer mixtures. The effects of the excess air ratio, solid conductivity, convective heat transfer coefficient and radiative properties are investigated.