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

Abstract

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.