Oxidation and combustion of the n-hexene isomers: A wide range kinetic modeling study

Abstract

A detailed chemical kinetic mechanism has been developed to study the oxidation of the straight-chain isomers of hexene over a wide range of operating conditions. The main features of this detailed kinetic mechanism, which includes both high and low temperature reaction pathways, are presented and discussed with special emphasis on the main classes of reactions involved in alkene oxidation. Simulation results have been compared with experimental data over a wide range of operating conditions including shock tube, jet stirred reactor and rapid compression machine. The different reactivities of the three isomers have been successfully predicted by the model. Isomerization reactions of the hexenyl radicals were found to play a significant role in the chemistry and interactions of the three n-hexene isomers. A comparative reaction flux analysis is used to verify and discuss the fundamental role of the double bond position in the isomerization reactions of alkenyl radicals, as well as the impact of the allylic site in the low and high temperature mechanism of fuel oxidation.3

Autoignition behavior of unsaturated hydrocarbons in the low and high temperature regions

“…1) at low temperature, the reactivity of large alkenes depends on the length of the saturated portions aside the double bond: longer alkyl chains determine shorter ignition delay times, as already discussed in previous works [15][16][17];…”

“…Direct elimination of HO 2 and diolefin formation is then preferred. Further details on this mechanism can be found in Mehl et al [16].…”

“…The first studies including a low temperature branching mechanism for alkenes were carried out by Mehl et al [16] in a joint collaboration between Milano and LLNL and by the Combustion group in Nancy [17][18].…”

“…The set of experiments provided by Vanhove is limited to temperatures lower than 850K. Mehl et al [16] computations predicted that at higher temperature the reactivity scale of the three isomers of hexene significantly changes.…”

Detailed chemical kinetic reaction mechanisms for primary reference fuels for diesel cetane number and spark-ignition octane number

“…Examples of improvements that will be included in the future include recent work of Taatjes et al [23] on alternative reaction pathways for reactions of alkyl radicals and O 2 to directly produce olefins via a concerted molecular elimination pathway will be implemented, and site-specific reactions of olefins can be improved following recent studies of Mehl et al [24] and VanHove et al [25].…”