Numerical study of the effect of CO 2 / H 2 O dilution on the laminar burning velocity of methane/air flames under elevated initial temperature and pressure

Diluents have an essential effect during combustion. Discovering the influence of CO 2 and H 2 O as diluents on laminar burning velocity (LBV) is helpful for combustion control and optimization. In this study, CH 4 /air/CO 2 /H 2 O mixtures were investigated and validated using the FFCM‐Mech 1.0 over extensive boundary conditions. The chemical effects of the diluents CO 2 and H 2 O were separated using a decoupling method. It was found that an increase in initial temperature promotes the chemical effects, while an increase in initial pressure does the opposite. In addition, the inhibiting effect of CO 2 on LBV is stronger than that of H 2 O. Sensitivity, mole fraction, and rate of production (ROP) analyses were used to reveal that the sum of the chemical effects of adding CO 2 and H 2 O separately was greater than the chemical effects of adding equal amounts of CO 2 and H 2 O simultaneously. This paper not only investigates the effect of CO 2 and H 2 O on the LBV under wide boundary conditions, but also offers a valuable guide for studying the operating conditions and intensity settings of exhaust gas recirculation (EGR) and theoretical guidance for further research on the combination of EGR and in‐cylinder water injection technology.