Influence of concentration gradient on methane-air explosion propagation: An experimental study

In underground coal mines, the methane distribution under actual conditions has a certain concentration gradient due to various factors such as air leakage and lower air velocity in local areas. In this paper, experiments were carried out to investigate the influence of the methane accumulation and concentration gradient on the methane-air explosion propagation. The experimental results show that in the process of methane explosion, the propagation distance of the flame and explosion wave in the rising stage are directly proportional to the methane accumulation. When the reaction time is less than a critical value, the flame propagation velocity and explosion overpressure with methane concentration distribution in the case of 9.5%-9.5%-3.5% are greater than those with a methane concentration change of 9.5%-9.5%-5.5%. However, when the methane concentration distribution is 9.5%-9.5%-0%, the flame propagation velocity and overpressure are less than those of the distributed methane in the working conditions of 9.5%-9.5%-3.5% and 9.5%-9.5%-5.5%.