An experimental investigation of ethylene/O2/diluent mixtures:: Laminar flame speeds with preheat and ignition delays at high pressures

The atmospheric pressure laminar flame speeds of premixed ethylene/O-2/N-2 mixtures were experimentally measured over equivalence ratios ranging from 0.5 to 1.4 and mixture preheat temperatures varying from 298 to 470 K in a counterflow configuration. Ignition delay measurements were also conducted for ethylene/O-2/N-2/Ar mixtures using a rapid compression machine at compressed pressures from 15 to 50 bar and in the compressed temperature range from 850 to 1050 K. The experimental laminar flame speeds and ignition delays were then compared to the computed values using two existing chemical kinetic mechanisms. Results show that while the laminar flame speeds are reasonably predicted at room temperature conditions, the discrepancy becomes larger with increasing preheat temperature. A comparison of experimental and computational ignition delay times was also conducted and discussed. Sensitivity analysis further shows that the ignition delay is highly sensitive to the reactions of the vinyl radical with molecular oxygen. The reaction of ethylene with the HO2 radical was also found to be important for autoignition under the current experimental conditions. (c) 2008 The Combustion Institute. Published by Elsevier Inc. All rights reserved.