Flame thickness and propagation characteristics of premixed methane-air explosion with a small filling ratio in an open-ended steel pipe

Through establishing a non-adiabatic open-ended steel pipe with a length of 20 m and a cross-sectional area of 0.08 m × 0.08 m, the changing rules of flame propagation and flame thickness of premixed methane/air explosion with a 10% fuel concentration and a 20% filling ratio were revealed. The experimental results show that the flame arrival time increased gradually with the increase of the distance from the ignition source, the maximum flame signal value initially increased along the pipe but then dropped. The flame thickness at a certain point could be measured by the time differences between vanishing moment and initial rising moment of flame signal at this point. With the increase of the distance from the ignition source, the flame thickness gradually decreased, the flame propagation speed presented a changing trend of increasing and decreasing, while the maximum overpressure followed a trend of decreasing, increasing and decreasing. The research results provide the scientific experimental basis for the reasonable setting mine explosion-resistant device, it is of great significance to effectively restrain the spread of explosion flame surface and avoid accident enlarging of gas explosion in coal mine.