Detailed and reduced chemical kinetic model of CH₄/air mixtures combustion based on high-precision first-principles molecular dynamics simulation

CH₄/air combustion reaction kinetics has attracted many research interests because of its wide application in engineering. In this work, the CH₄ oxidation in O₂ at high temperatures is simulated based on the first-principles molecular dynamics method first time. Two new intermediates, HCOOH and O₃, and their effect on the CH₄ oxidation are revealed. Specifically, adding HCOOH-related reactions into current model GRI 3.0, NUIG 1.1 and USC II may significantly improve their predictions on the premixed laminar flame speed of CH₄/air mixtures. Elementary reaction analysis also discovered that radicals, such as OH, HO₂, and others play key roles in CH₄ oxidation. These radicals act as highly active oxidants and promote final product formation. Combining elementary reaction with simplifying technique, a novel First-Principle (FP) and 30-step Reduced-FP (R-FP) chemical kinetic model are constructed. By using our two models, the ignition delay time, species concentration in flow reactor and premixed laminar flame speed of premixed reactive mixture (CH₄/O₂/Ar, CH₄/O₂/H₂O/N₂ and CH₄/air) combustion are successfully predicted and verified by comparing with experimental results. In general, the FP and R-FP models will be advantageous for application of engineering in the future.