Influence of the tunnel wall surface condition on the methane-air explosion

Based on numerical methods and theoretical analysis, the influence of the tunnel wall surface conditions on the methane-air explosion is evaluated. A rough tunnel wall causes stronger turbulence in the methane-air explosion. In a straight tunnel where some part of the space is filled with the methane-air mixture, the turbulence intensity varies with distance along the tunnel axis: it is higher in the methane-air premixing region and also in the far region of air shock wave propagation; between these regions, the turbulence intensity is lower. In the methane-air premixing region, the effect of turbulence is manifested as a significant increase in the explosion pressure. In the far region of air shock wave propagation, turbulence makes the shock wave strength decrease, but its effect is indistinctive among others. In the original methane-air premixing region, the explosion pressure of the methane-air mixture in a tunnel with rough walls is higher than that in a tunnel with smooth walls. However, the air shock wave beyond the premixing region in a tunnel with rough walls is weaker than that in a tunnel with smooth walls.