The inhibition/promotion effect of C₆F₁₂O added to a lithium-ion cell syngas premixed flame

The objective of this study is to investigate the impact of different fractions (0–0.05) of C₆F₁₂O addition on laminar flame speed of hydrocarbon syngas by varying the fuel/oxidizer equivalence ratio (0.6–1.2) using Bunsen burner method. The determination of the syngas composition comes from the venting gas of lithium-ion cell during thermal runaway. It is found that C₆F₁₂O is significantly more effective at stoichiometric and fuel-rich conditions compared to lean flames regardless of fuel species, which implies more suitable for syngas/air flame inhibition than CH₄. The laminar flame speeds of syngas/air increased with lower concentration (<0.01) of C₆F₁₂O when equivalence ratio less than 0.67, while it decreased with arbitrary concentration of C₆F₁₂O at the condition of equivalence ratio not less than 0.67 due to the increased heat release rate by exothermic reaction involving C₆F₁₂O. The laminar flame speed was more sensitive to C₆F₁₂O addition at stoichiometric and fuel-rich conditions due to the inhibitory effect of substances containing fluorine. Comparison between experimental and numerical results shows a better agreement under fuel-lean conditions with lower C₆F₁₂O additions using a modified mechanism derived from USC Mesh II. Thermodynamic equilibrium calculations and sensitivity analyses are showed separately that the variation of flame radical concentrations is consistent with laminar flame speeds and the lean flames are more sensitive to the reactions containing fluorine compared to rich for syngas/air flame with C₆F₁₂O addition.