Additive Effects on the Burning Velocity of Ethylene–Air Mixtures

Abstract

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, N2, and CO2) (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 flame 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.

Normal burning velocity and propagation speed of ethane–air: Pressure and temperature dependence

“…The overall reaction orders are only slightly influenced by the initial temperature, especially when the stoichiometric ethane- air mixture is examined. For the other mixtures, they range within 1.40 and 1.76, similar to other gaseous fuel-air mixtures (ethylene [58], propene [59]). Much smaller reaction orders, between 0.94 and 1.45, have been found for ethane-air using the burning velocities determined by means of burned mass fraction [9].…”

“…Similar diagrams were obtained for the examined mixtures at all initial temperatures. The data were analyzed according to a power law equation following similar approaches [49][50][51][52]58]: Table 2. The baric coefficients of burning velocities at 298 K range within À0.28 and À0.12, typical values for hydrocarbon-air mixtures.…”

The development of a new optical method to measure the delay time of spark ignition

“…It relies on the detailed analysis of the early stages of flame propagation. The use of the third power law of pressure increase during these stages, ∆P, combined with an improved statistical analysis of experimental data, resulted in a new method to evaluate the normal burning velocity and suggested the existence of an ignition delay time, τ, defined as a time interval between the ignition energy deposition and the beginning of steady flame propagation [21][22][23][24][25][26][27]:…”

“…The method was validated either by comparing the resulted parameters with those reported in literature [21][22][23][24][25][26][27][28], or by analysing also the time evolution of emitted radiation within the same time interval [29].…”

Explosion of gaseous ethylene–air mixtures in closed cylindrical vessels with central ignition

“…Explosion vessels S, C1 and C2 were previously described [24,25,30,31]. Each vessel was equipped with several ports for the gas feed/evacuation valve and for mounting the ionization probes, thermocouples, pressure transducers and ignition electrodes.…”