Experimental study on ethane ignition delay times and evaluation of chemical kinetic models

The ignition delay times of ethane were measured using a high-pressure shock tube at different pressures (p = 1.2, 5.0, and 20.0 atm) and equivalence ratios (φ = 0.5, 1.0, and 2.0) with different argon diluent ratios. Correlations of the measured ignition delay times were provided. The measurements were compared to calculations from several representative chemical kinetic models to evaluate their performances. Results showed that Aramco Mech 1.3 could well reproduce the measured ignition delay times over a wide range, while GRI Mech 3.0 significantly overpredicted the measurements at stoichiometric and high equivalence ratio. To find out the reasons for the differences and similarities of the mechanisms on calculating the ignition delay time of ethane, sensitivity analysis and reaction pathway analysis were conducted. It is observed that the mechanisms have similar pathway for ethane consumption, while they have significant differences for ethyl radical decomposition reactions. Results also indicated that the incompleteness of the C₂H₅ + O₂ reaction channels and the underestimation of the rate constant of reaction C₂H₄ + H (+M) = C₂H₅ (+M) might be responsible for the overestimation of GRI Mech 3.0 on ethane ignition. The mechanisms studied give similar prediction at a high equivalence ratio because reactions with a significant difference on rate constants do not show a high sensitivity coefficient at the condition.