Study on the effect of venting conditions on methane-air explosion characteristics in full-scale mine tunnel

The overpressure and heat products generated by methane explosions seriously threaten human life. Therefore, studying the influence mechanism of venting conditions on methane explosion characteristics in full-scale tunnels is of great significance for preventing and controlling methane explosions in mines. This study takes the Lynn Lake experimental mine (LLEM#501) as a background case, and studies the changes in methane explosion characteristics under different sealing ratios in full-scale tunnel using the GASFLOW-MPI code. The study shows that the greater the sealing ratio, the larger the maximum overpressure, maximum fluid velocity, and reflection wave overpressure in the methane explosion area. As the sealing ratio increases, the coupling effect of gas expansion and reflected shock wave overpressure causes a decrease in both the negative pressure value and the negative pressure area in the explosion zone. When the area is completely sealed, there is no formation of negative pressure. High-temperature heat products and flame backflow by cavity structures is the main factor that causes local temperature anomalies to increase and oscillations. Heat loss is a crucial factor influencing methane explosions, with approximately 22.75 % to 25.77 % of the explosion energy being dissipated in the form of heat during the explosion process. As the sealing ratio increases, the heat loss during the explosion process shows an exponential decrease trend. By analyzing the methane explosion energy equation, it has been determined that the decrease in heat loss during the methane explosion process is the primary cause for the increase in methane explosion overpressure and velocity.