Study on the Flame Propagation Characteristics of Multi-point Methane Explosions in Long and Narrow Confined Spaces

To investigate the injuries caused by multi-point gas deflagration accidents within the complex environment of a mine, this paper conducts a numerical study of the flame propagation of methane explosions in a ventilation door and supporting structures. The effects of ignition source position, number, and changes in the state of the ventilation door were analyzed based on explosion simulation with three different ignition source settings. The results show that the interplay between the increased number of ignition sources and the confining effect of the flame significantly affected the structural evolution of the flame. After crossing the ventilation doors, the flame structure transitions to forms such as umbrella flame, columnar flame, tip flame, or twisted flame. In the early stages of flame propagation, reflected pressure waves are the main cause of changes in flame propagation velocity. As the reaction proceeds, the cause changes to an interaction between the turbulent flame, the chemical reaction, and the reflected pressure wave. The speed of a single ignition source passing through the ventilation door was 172.5 m/s, while the speeds of two ignition sources at increasing distances were 146.6 m/s and 115 m/s, respectively. Therefore, the speed of the flame passing through the ventilation door is inversely proportional to the number of ignition sources and inversely proportional to the distance between the ignition sources. Additionally, with two-point fire sources, the more distorted the vortex distribution, the more twisted the flame propagation shape. This study addresses the lack of research on the flame propagation characteristics of methane explosions in long and narrow confined spaces, which is crucial for gas explosion risk prevention.