Numerical Simulations of the Influence of Inert Gases (N2/CO2) on Combustion Characteristics of Laminar-Premixed Biosyngas Flame.

Abstract

In this work, the influence of different N2/CO2 contents (up to 60% in fuel volume) on combustion features of laminar-premixed CO/CH4/H2 flame with various equivalence ratios (0.6–1.6) at standard conditions was numerically calculated using ANSYS CHEMKIN-PRO with the GRI-Mech 3.0 mechanism. The mole fraction profiles of the major species and the rate of production of dominant elementary reactions in the flames of CO/CH4/H2/N2/CO2/air were obtained. The effect of inert gas addition on the formation of NOX, H, O, and OH was analyzed, and the sensitivity coefficient of the active radical mole fraction was obtained. The results suggest that the addition of inert gas of the fuel mixture with various equivalence ratios reduces laminar burning velocity and adiabatic temperature, which have always had a good positive correlation and the maximum peak point shifted left. CO2 has obvious inhibitory effect on the formation of NO by reducing the amount of O radicals and obstructing the conduct of the reaction of NNH + O ⇔ NH + NO, but it promotes the formation of NO2 mainly through the reaction HO2 + NO ⇔ NO2 + OH. The reactions H + O2 + H2O ⇔ HO2 + H2O, H + O2 ⇔ O + OH, and OH + CO ⇔ H + CO2 are three very important reactions for the molar fractions of H, O, and OH that decrease significantly with an increase of inert gas concentration.