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

Abstract

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.