CH₄/Air 대향류 비예혼합화염에서 CO₂의 소화효과에 대한 재고찰

초록

The suppression of low strain rate CH₄/air nonpremixed flames was studied numerically to revisit the extinguishing effects of CO₂ using a counterflow configuration. Considering that thermal radiation played an important role on the flame structure and extinction limits in low strain rate nonpremixed flames, a comparison of representative radiation models was first conducted in terms of extinction limits with CO₂ as fire extinguisher. As a result, the critical CO₂ volume fractions in the oxidizer stream required to extinguish the flames were in good agreement with the experimental data reported in the literature by applying both statistical narrow band (SNB) model and optically thin model (OTM), while somewhat under-prediction by the OTM was observed with CO₂ diluted in the fuel stream. The surrogate agents were adopted to estimate the quantitative contribution on the flame extinguishment among pure dilution effect, radiation effect, thermal effect excluded the radiation effect and chemical effect due to the CO₂ dilution in the fuel or oxidizer stream. This systematic numerical strategy provided a detailed insight into the extinguishing mechanism of low strain rate nonpremixed flame by CO₂ fire extinguisher.