Ignition and Oxidation of Ethylene-Oxygen-Diluent Mixtures with and Without Silane

Several dilute mixtures of varying concentrations and equivalence ratios (phi=0.5,1.0) of C2H4/O2/Ar/SiH4 were studied between 1115-1900 K and 0.9-3.3 atm. Argon dilution ranged from 96-98% with total concentrations between 0.67 and 3.2 x 10-5 mol/cm3. Reaction progress was monitored using chemiluminescence emission from the hydroxyl radical near 307 nm. For SiH4 concentrations less than 10% of the ethylene in the mixture by volume, the ignition delay time was reduced by approximately 30% to greater than 50%. The addition of SiH4 had a small effect on ignition activation energy, indicating the chain branching mechanism for C2H4 ignition is sped up but not altered greatly by the silane at higher temperatures. After adding an appropriate OH* submechanism, several modern kinetics mechanisms containing high-temperature ethylene chemistry were compared to the data without SiH4. Most of the mechanisms captured the ignition activation energy quite well, but only the mechanism of Wang and Laskin (1998) was typically within 10% of the absolute experimental ignition times over the entire range of conditions. The basic formation and quenching characteristics of the OH* profiles were reproduced by most mechanisms, but each requires some improvement to match all features.