Flame and Blast-Wave Propagation of Premixed Methane/Air Explosions in Nonuniform Porous Networks Filled by Inert Glass Balls

Porous media are widely used in fire or explosion suppression and combustion, which are mainly determined by material properties and geometric parameters. In the present work, we constructed a porous network by stacking glass balls of different diameters and experimentally investigated the effect of the porous network on flame and blast-wave propagation of premixed methane/air explosions. The results show that flame propagation characteristics in pore networks are significantly influenced by three key factors: equivalent pore size (De), pore zone length, and methane concentration. Pores exhibit flame-accelerating effect, which is particularly pronounced when De is 2.74 mm. In contrast, pore zones with De of 1.10 mm exert an inhibitory influence on explosion propagation. Increase of pore zone length enhances the overpressure suppression effect, with the peak overpressure reduction rate (Rp) attaining a maximum of 61.99%. However, the suppression effect becomes negligible when the equivalent pore size (De) is 1.10 mm. Additionally, within the pore zone, flame propagation speed, overpressure magnitude, and speed increment all increase first and then followed by subsequent decrease with increase of methane concentration, and their peak values are observed at a methane concentration of 10%.