Additive Effects on the Burning Velocity of Ethylene-Air Mixtures

摘要

Using a simple correlation based on the cubic law of early pressure rise during a closed vessel explosion, the laminar burning velocities of the stoichiometric ethylene-air mixture diluted with several additives (Ar, N_2, and CO_2) (concentrations between 4 and 40 vol %) were calculated from pressure-time records, at total initial pressures between 0.2 and 1.2 bar and ambient initial temperature. These are important input properties for numerical modeling of explosion propagation in closed or vented enclosures and for safety recommendations concerning the necessary inert gas addition. The decrease of burning velocities determined by the increase of the total initial pressure and inert gas addition is examined. A computational study of free laminar premixed flames of ethylene-air in the presence of the same additives based on the use of 53 species and an extended reaction mechanism with 592 elementary reactions delivered the temperature and species profiles in the Hame front, together with the flame width and burning velocity. Both the computed and the experimental burning velocities versus the additive concentration follow the same trend, explained by the influence of additives on the overall reaction rate between fuel and oxidant in the reaction zone and heat- and mass-transfer rates between the burned and unburned gases. The differences observed between computed and experimental burning velocities are small and can be assigned to both unavoidable scattering of available measurements and the mechanism used for numerical simulations.