Energy & Fuels, Vol.29, No.10, 6768-6779, 2015
Effects of Exhaust Gas Dilution on the Laminar Burning Velocity of Real-World Gasoline Fuel Flame in Air
The effects of exhaust gas recirculation (EGR) on the laminar burning velocity of a commercial gasoline fuel-air mixture have been studied both numerically as well as experimentally at atmospheric pressure. The experiments have been performed using the heat flux burner method. For numerical simulation, a binary mixture of 95% iso-octane and 5% n-heptane (PRF95) is assumed to be the surrogate for the real world gasoline fuel. The numerical simulations have been carried out using a skeletal mechanism comprising of 171 species and 861 reactions for primary reference fuels. A correlation of laminar burning velocity of the commercial fuel is suggested based on experimental data for different EGR dilutions. The results show that the reduction in the laminar burning velocity caused by the EGR dilution can be recovered by the increase in the unbumt gas temperature. However, the rise in the unburnt gas temperature results in a trivial rise in the adiabatic flame temperature. The increase in the laminar burning velocity due to elevated unbumt gas temperature is principally attributed to the increase in thermal diffusivity of the fuel-air mixture, while the reaction rate has only a minor influence. The presence of CO2 in the EGR influences the chemistry of the flame along with diluting it. Under stoichiometric conditions, the chemical and dilution effects toward the reduction in laminar burning velocity are almost equal.