Influence of CO₂ injection parameters and layout on flame suppression effect of gas explosions

Current research on CO₂ explosion suppression mainly focuses on parameters such as peak explosion pressure and flame propagation speed, while studies on changes in free radicals and turbulence distribution during CO₂ suppression of methane explosions are relatively limited. This study systematically investigates the explosion propagation characteristics of methane premixed gas within gas drainage pipelines and the suppression mechanism of CO₂ under different injection pressures, nozzle layouts, and control sequences, through a combination of theoretical analysis, experimental research, and numerical simulation. Experiments were conducted using a self-built medium-scale explosion shock tube system, combined with flame sensors and spectroscopy techniques to capture flame characteristic parameters and typical evolution patterns of free radicals. A chemical kinetic model of methane explosion was developed based on CHEMKIN-PRO software to qualitatively and quantitatively analyze the inhibitory effects of CO₂ on key free radicals. The results showed that when the nozzle flow rate was 6.38 m³/s, the maximum reduction in flame propagation speed reached 79.3%. The flame signal intensity showed a notable decrease, and the molar fraction of ·OH radicals decreased by 14.7%. The local turbulence intensity peak (about 20%) formed by high-pressure injection significantly improved CO₂ diffusion efficiency and enhanced suppression effects. The dual-nozzle staggered inclined injection strategy achieved the best effect. By employing a spatiotemporal coupling design, it simultaneously controlled both the injection quantity and timing of the suppressant. This approach established a triple barrier of "physical dilution–chemical inhibition–dynamic interception," resulting in a 47.64% reduction in the molar fraction of ·OH radicals, significantly outperforming traditional single-nozzle and other dual-nozzle schemes.