Numerical analysis on the effects of CO2 dilution on the laminar burning velocity of premixed methane/air flame with elevated initial temperature and pressure

Abstract

Understanding the different effects of CO2 dilution on the laminar premixed flame is an effective strategy for combustion control. Thus, a chemical kinetic modeling study of laminar burning velocity (LBV) for CH4/air/CO2 mixtures coupling with a detailed chemical reaction mechanism was employed under a wide range of initial conditions. After validation and comparison, the FFCM 1.0 was selected for this study. Based on the numerical prediction of LBV, the decoupling method was carried out to separate the effects of diluent CO2, including dilution, thermal and chemical effects, whose variations show that the rising initial temperature facilitates the three effects whereas the elevated pressure shows the opposite impact. In order to explain the particular process physically and chemically, the parameters analysis, sensitivity analysis and mole fraction analysis methods were conducted, and the LBV enhancement made by per unit of fuel, relevant thermal parameters and the important active radicals were proved to be responsible for the variation of the three effects, respectively. Furthermore, the domain reactions contributing to chemical effect are reactions (R32) and (R62), respectively, as temperature and pressure vary. Through this work, it not only completes the research on the effect of CO2 dilution on the laminar premixed flame, but also expands the commonly exploring initial conditions to a wide range, which provides the reference for the research on the operation condition and intensity setting of exhaust gas recirculation (EGR).