Explosion behavior of non-uniform methane–air mixtures under different ignition positions in half-open vertical pipes

The explosion behavior of non-uniform methane–air mixtures in semi-confined environments is a critical concern in energy safety, particularly in industries involving natural gas storage, transportation, and processing. This study investigated the explosion dynamics of non-uniform methane–air mixtures in half-open vertical pipes, emphasizing the impact of ignition position. The results demonstrate that the ignition position significantly influences explosion characteristics. Specifically, the maximum rate of overpressure increase was higher when ignition occurred at the center, compared to the top or bottom, under identical conditions. This variation was attributed to differences in concentration distribution within the pipe and rupture shape at the relief vent, which influenced external gas to reentry the pipe and altered the internal gas distribution. Moreover, the growth rates of relative velocities at different ignition positions were analyzed along with the gravitational effects on explosion propagation. These findings offer valuable insights for improving the safety design and operational protocols in flammable gas systems, helping mitigate explosion risks in semi-confined spaces.