Combustion Enhancement and Inhibition of Methane Flame by HFC-236fa

Currently, the use of “halon” fire extinguishing agents has been banned due to their detrimental effects on the ozone layer, making it imperative to find a fire extinguishing agent that offers both high performance and environmental friendliness. However, the fire suppression mechanisms of certain halogenated hydrocarbon agents remain inadequately understood, hindering their development and evaluation. In this study, we focused on the inhibition effect of HFC-236fa and HFC-227ea on methane flames. The experimental results show that the inhibition effect of HFC-236fa was better than that of HFC-227ea by reducing the burning velocity from 18.67 cm/s to 5.45 cm/s at φ = 0.7. At φ = 1.0, the inhibition effects were comparable when the addition amount was less than 0.01, but as the addition amount was further increased, the inhibition effect of HFC-227ea was better than that of HFC-236fa, and the inhibition effects of HFC-236fa and HFC-227ea were close to each other at φ = 1.2. And we analyzed its dynamics using CHEMKIN software. We conducted a comprehensive analysis of the laminar burning velocity, chemical reaction rate, chain radical generation and consumption rates, sensitivity analysis, and reaction pathway analysis. The results indicate that HFC-236fa exhibits better inhibition effects on lean flames compared to HFC-227ea. Sensitivity analysis revealed that the primary flame inhibition reaction for HFC-236fa is CF3CH2CF3 → CF3CH = CF2 + HF, with the reaction products playing a significant role in scavenging chain free radicals in subsequent reactions. In contrast, HFC-227ea predominantly produces CF3-CHF through C-C bond cleavage, generating CF3 free radicals that contribute to the scavenging process. Additionally, the reaction pathway analysis showed that HFC-236fa releases a greater quantity of CF3 free radicals than HFC-227ea, which more effectively captures H and OH free radicals during flame combustion, resulting in enhanced inhibition performance.