Pore-scale study of flame propagation and thermal characteristics in randomly packed beds

The discrete element software LIGGGHTS is applied to reproduce the packing process of pellets under gravity. A 3-D geometric model is obtained which is similar to the actual packed structure. Based on the 3-D geometric model, a Large-eddy simulation (LES) method combined with the power-law flame wrinkling model is utilized to simulate the hydrogen-air premixed combustion in enclosed space. In addition, the validity of the model is verified by comparing the simulation results with the experimental data. It shows that the expansion velocity of high-temperature region in the porous structure is higher than that in the non-porous structure. At the initial ignition stage, as the difference of temperature is too large, the temperature transition zone can be widened effectively by the porous media structure, and the temperature gradient is reduced leading to a more uniform temperature field. According to the distribution of Karlovitz number on the flame surface, the quantitative analysis of turbulence-flame interaction in the porous structures is carried out, and the zoning law of turbulent flame under various operating conditions is established.