抄録
Porous media burners in comparison with free flame burners have major benefits such as higher thermal efficiency, stable flame in a wider range of stoichiometric ratios and feed flow rates, capability of using low calorific fuels and low production of pollutants. In the present study, premixed and laminar combustion of hydrogen in a solid matrix with spongy lattice is simulated. The axisymmetric solid matrix is considered to be inert, isotropic and homogenous in the unsteady simulations. The burner consists of a divergent inlet followed by a constant area section. A multi-step chemical kinetics is implemented. Heat exchange between the solid and gas phases is simulated using an experimental correlation for volumetric convective heat transfer coefficient, and the diffusion approximation is used to simulate the radiation mechanism inside the solid matrix. All physical properties of the gas mixture are considered as functions of local temperature and mixture composition. The governing equations are discreted and solved by the control volume scheme and SIMPLE algorithm. The effects of certain parameters such as flow rate and physical properties of the solid matrix on the thermal/stability performance of the burner are analyzed. Increasing the feed flow rate causes upstream movement of the flame front and increase in the flame temperature and pollutant formation. The flammability limits are obtained in the range of stoichiometric ratios between 0.5 and 1.2, where the widest belongs to a stoichiometric mixture.
