Energy & Fuels, Vol.26, No.8, 4887-4895, 2012
Autoignition of Methyl Decanoate, a Biodiesel Surrogate, under High-Pressure Exhaust Gas Recirculation Conditions
The autoignition of methyl decanoate, a standalone biodiesel surrogate or surrogate component, is studied under high-pressure exhaust gas recirculation (EGR) conditions relevant to internal combustion engines. Ignition delay times were determined in reflected-shock experiments using measured pressure and electronically excited OH chemiluminescence for stoichiometric methyl decanoate/air/EGR mixtures containing 0-60% EGR at 900-1300 K and 20 and 50 atm. Ignition delay time dependence upon pressure and EGR fraction was found to obey tau alpha P-0.8 tau alpha (1- EGR %/100)(-1) for the conditions studied. Experimental results are compared to three comprehensive kinetic models for methyl decanoate oxidation from the recent literature: Herbinct et al. (Herbinet, O.; Pitz, W. J.; Westbrook, C. K. Combust. Flame 2008, 154, 507-528 and Herbinet, O.; Pitz, W. J.; Westbrook, C. K. Combust. Flame 2010, 157, 893-908), Glaude et al. (Glaude, P. A.; Herbinet, O.; Box, S.; Biet, J.; Warth, V.; Battin-Leclerc, F. Combust. Flame 2010, 157, 2035-2050), and Dievart et al. (Dievart, P.; Won, S. H.; Dooley, S.; Dryer, F. L.; Ju, Y. Combust. Flame 2012, 159, 1793-1805). Model-experiment comparisons are generally favorable, with some differences in model performance because of variations in C-0-C-2 chemistry, of predominate sensitivity at the conditions studied, and methyl decanoate hydrogen-atom abstraction rates. Ignition delay times for stoichiometric mixtures containing EGR, defined as the complete products of combustion, and synthetic EGR, defined here as pure N-2, are indiscernible, indicating that the primary influence of EGR is to simply displace fuel and O-2, thereby decreasing radical branching, a conclusion that is supported by the kinetic models.