Explosion propagation characteristics of gas and air under segmented distribution in sealed pipelines

Abstract

In confined mine roadways, gas and air commonly form a segmented distribution. To investigate the characteristics of explosion propagation under such conditions, experiments were conducted with varying air and gas segment lengths and different gas concentrations, using a self-designed explosion propagation simulation system. Flame propagation behavior, peak overpressure, and explosion mechanisms under uniform and segmented gas and air distributions were systematically investigated. Results show that, under gas and air segmented distribution, flame propagation undergoes four distinct stages: spherical, finger-shaped, planar, and tulip-shaped. When the air segment is longer than the gas segment, the flame front cannot reach the sealed end due to insufficient fuel. Within a certain range (0.5–1.5 m), increasing air segment length delays the effect of reflected pressure waves on the flame front, weakening suppression and increasing propagation distance. Longer gas segments and higher gas concentrations result in more combustible gas, extending flame propagation. Furthermore, due to the oxygen replenishment effect from the air segment, increasing gas concentration within the 8 %-11 % range continuously raises the peak overpressure at the closed end, with 11 % producing higher values than 9.5 % and 8 %. The findings provide a valuable reference for assessing the risk of methane explosions in sealed mine roadways.