Study on inhibition of methane explosion by critical premixing ratio of carbon dioxide under action of porous materials

To explore the efficient explosion suppression technology for coal mine gas drainage pipelines and ensure the safe transportation of gas in such engineering during coal mining, an investigation is conducted on the influence of gas-solid synergistic action modes under different premixing ratios of carbon dioxide （0%, 4%, 8%, 12%, 16%） on the combustion and explosion characteristics of methane. This paper utilizes a square pipe with dimensions of 100 cm × 10 cm × 10 cm, with porous foam copper installed at a distance of 40 cm from the ignition end, having an average pore diameter of 2.54 mm. Experimental results demonstrate that the premixing ratio of carbon dioxide has a relatively small impact on the development of the methane flame structure under porous materials, but it exerts an effective inhibitory effect on the flame propagation process. With an increase in the premixing ratio of carbon dioxide, both the critical velocity and maximum velocity of the flame decrease. The inhibition ratio of carbon dioxide with a premixing ratio of 16% on the critical velocity amounts to 73.19%, while the inhibition ratio on the maximum velocity can reach 81.75%. Furthermore, the explosion pressure decreases in the upstream and downstream sections of the pipeline as the premixing ratio of carbon dioxide increases. The suppression ratio of the maximum explosion pressure in the upstream and downstream sections can reach 87.44% and 94.79%, respectively. Based on these findings, it is concluded that the critical premixing ratio of carbon dioxide and porous foam copper in terms of coupling inhibition is 11%. This study suggests that when designing safety protection facilities for gas drainage pipeline engineering and utilizing porous materials and carbon dioxide to inhibit gas explosions, the critical premixing ratio of carbon dioxide should be maintained above 11%, effectively preventing gas explosions. These experimental results also provide theoretical support for the development of efficient suppression techniques for combustible gas explosions in pipeline engineering.