Porous medium combustion is recognized for its high thermal efficiency, low pollutant emissions, and superior flame stability. However, the pore-scale mechanisms governing convection-radiation coupling and flame morphology remain insufficiently understood. This study investigates premixed methane-air combustion within a randomly packed bed of Al 2 O 3 spheres through pore-scale numerical simulations. The k-ε turbulence model, combined with the Eddy Dissipation Concept for combustion chemistry and the Discrete Ordinates model for radiative transfer, is employed. A systematic sub-domain scaling analysis identifies the N = 3 configuration, a symmetric segment scaled to three times the particle diameter, as the optimal trade-off between predictive fidelity and computational cost. Simulations for three pore Reynolds numbers (250, 350, 450) elucidate the characteristics of convection-radiation coupling within porous media combustion. Increased Re p enhances convective transport, shifting the flame front downstream, while radiation reinforces upstream heat recirculation. Quantitatively, radiation attenuates the mean gas temperature by up to 8.1% but amplifies the peak heat flux by approximately 90% and 59% at Re p = 250 and 350, respectively. Besides, the peak heat release rate exhibits a non-monotonic trend, and the axial radiation flux intensifies substantially across the burner, with increments of 45.8% and 11.2% as Re p increases from 250 to 450. The findings offer mechanistic guidance of heat recirculation and flame stability within porous media combustion for the industrial applications of porous burners.
Xu et al. (Sun,) studied this question.