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With the advent of energy crisis and stringent emission regulations, natural gas (NG)/diesel dual‐fuel engines have entered the popular view. In this paper, the accurate boundary conditions are determined by the Converge model and the transient parameters were introduced into the chemical kinetics model to make the operating conditions more closely match the actual engine operating conditions. The effects of different methane/n‐heptane ratios, initial temperatures, initial pressures, and equivalence ratios on the IDT of methane/n‐heptane fuel mixtures were analyzed using comprehensive chemical kinetic tools such as mole fraction analysis, ROP analysis, and sensitivity analysis. The IDT of methane/n‐heptane mixture decreased significantly with increasing the equivalence ratio, initial pressure, and the proportion of n‐heptane in the mixture, but the change of temperature was more complicated for the IDT. The NTC behavior of methane/n‐heptane mixture was also affected by the NTC behavior of n‐heptane. With the increase of initial temperature, the consumption of methane and n‐heptane appeared to be significantly accelerated. The peak of radicals and intermediate groups appeared earliest and had the highest radical concentration when the n‐heptane content was 30%. With the increase of initial pressure, the peak moments of the six radicals were further advanced, but the mole concentrations of O, OH, H radicals decreased significantly. This paper not only provides a reference for the design of NG/diesel dual‐fuel engines, but also provides a theoretical basis and data support for improving the ignition and initial condition setting strategies of the engines.

Diluents have an essential effect during combustion. Discovering the influence of CO2 and H2O as diluents on laminar burning velocity (LBV) is helpful for combustion control and optimization. In this study, CH4/air/CO2/H2O mixtures were investigated and validated using the FFCM‐Mech 1.0 over extensive boundary conditions. The chemical effects of the diluents CO2 and H2O 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 CO2 on LBV is stronger than that of H2O. Sensitivity, mole fraction, and rate of production (ROP) analyses were used to reveal that the sum of the chemical effects of adding CO2 and H2O separately was greater than the chemical effects of adding equal amounts of CO2 and H2O simultaneously. This paper not only investigates the effect of CO2 and H2O 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.