Study on the thermal and mass evolution behavior of methane air premixed gas under rigid and flexible obstacles

There has been a lack of public reports on the combustion and explosion risks under the coupling effect of different structural materials in coal mine tunnels. Therefore, this article uses a square pipe-line with a cross-section of 0.01 m2 and a length of 1 m to study the methane combustion and explosion process under different blockage rates and rigid and flexible obstacle arrangements, in order to fully reveal the impact of tunnel construction on explosions. The results indicate that when a rigid obstacle is in the forward position, the blockage rate of a flexible obstacle is positively correlated with the flame contact velocity, maximum velocity, and maximum explosion pressure inside the pipe-line. When placing a flexible obstacle in the front, as the blockage rate of the flexible obstacle increases, the contact speed and maximum speed first increase and then decrease. As the blockage rate of flexible obstacles increases, the maximum upstream explosion pressure first decreases and then increases, while the total pressure inside the pipe-line first increases and then decreases. When flexible and rigid obstacles are combined and placed, they both increase heat transfer, convection, and radiation inside the tube, indirectly reducing the risk of hot air caused by explosions. Under the premise of a flexible obstacle blockage rate of 0.4, the maximum downstream overpressure can reach 2.96 times that of the upstream area, providing data support and theoretical reference for the safe lay-out of explosion-proof structures and equipment.