Coupled behavior of overpressure and vented flame in large-scale constrained spaces during methane deflagration: Effect of ignition position

To effectively mitigate the risks of explosions caused by gas leaks and to understand the dynamic evolution of accident occurrences, this study utilizes a self-constructed large-scale experimental platform to investigate the characteristics of gas deflagration and venting in confined spaces under various ignition conditions. The results indicate that the venting path of the flame is closely linked to the ignition position. When ignition occurs at the top, middle, or bottom, the external flame vents first from the corresponding location: top, middle, or bottom, respectively. The intensity of the explosion varies depending on the ignition position, ranked in the following order: middle ignition > top ignition > bottom ignition > vent end ignition > closed end ignition. Mid-position ignition results in the highest indoor overpressure and external flame propagation speed, reaching 36.62 kPa and 156.79 m/s, respectively. There is a significant correlation between the peak indoor overpressure and the maximum outdoor flame propagation speed, which aligns with the Boltzmann function relationship. Compared to the EN 14494 prediction formula, the NFPA 68 prediction formula is more suitable for forecasting the maximum venting distance of the external flame. The findings of this study provide essential theoretical insights and data support for preventing gas explosion incidents in both industrial settings and everyday life, as well as for investigating the causes of such accidents.