Effect of Porous Materials on Explosion Venting Overpressure and Flame of CH₄/air Premixed Gas

To understand the overpressure transient and flame behavior of CH₄/air premixed gas explosion venting in the presence of porous materials, a series of explosion venting tests is conducted in a spherical vessel with a neck. The effects of pore size, porosity, thickness, and properties of porous material on P_stat, P_red, P_burst, and P_ext are measured using pressure transmitters, and the image of an exploding venting jet flame passing through porous materials is captured using a high-speed camera. It is shown that the pressure wave at the high-pressure side of the explosion vent is in a critical state when the venting burst membrane ruptures without the porous materials, and the vented jet is confirmed to be under-expanded. The addition of porous materials does not significantly affect P_stat but results in the highest P_burst in porous material Al₂O₃ 50PPI and the highest P_red in porous material SiC 20PPI. This is consistent with the assumption that P_red > P_burst, and that an increase in P_burst corresponds to a decrease in P_red. In addition, P_ext is more likely to occur at a position 250–350 mm away from the vent, and as the thickness of the porous materials increases, the possibility of an external explosion overpressure will increase. Moreover, the porous material significantly affects the venting jet flame, and as the thickness of the porous material increases, the shape of the venting jet flame resembles that of a “broom,” owing to the dynamic overpressure generated from the flame-porous material interaction.