Inhibition effect and kinetics studies on the deflagration characteristics of hydrogen compressed natural gas (HCNG) by C6F12O and CO2

Abstract

To explore the effects and underlying mechanisms of C₆F₁₂O and CO₂ on the explosion suppression of hydrogen compressed natural gas(HCNG), this study investigates its deflagration characteristics under various hydrogen concentrations (0–30%) and equivalence ratios ($\phi$ = 0.6–1.4) by using CHEMKIN. A suppression mechanism for C₆F₁₂O to HCNG combustion, consisting of 222 species and 1744 reactions is proposed. Findings show that, C₆F₁₂O outperforms CO₂ in flame suppression, demonstrating 2.25 times greater flame thickness inhibition, 5 times reduction in laminar burning velocity, 6.57 times lower adiabatic flame temperature, and 5 times more effectiveness in reducing heat release rate. Further analysis demonstrated that the adiabatic flame temperature linearly correlated with the volume fractions of C₆F₁₂O and CO₂. Furthermore, the flame thickness, laminar burning velocity, maximum heat release rate, adiabatic flame temperature, sensitivity factors, and molar fractions of reactive radicals decreased with increasing the proportion of C₆F₁₂O and CO₂. The results show that CO₂ primarily acts through physical dilution, whereas C₆F₁₂O dominates through chemical suppression, as free radicals are captured by fluorides. The C₆F₁₂O's major suppression reactions are: R830:CFO + HCO + HF, R833:CF₃+OCF₂O + F, and R925:CF₂+OHCF:O + HF. Findings will provide new insights for the prevention of HCNG explosions and reduce hazardous effects.