Effect of stereoisomeric structure and bond location on the ignition and reaction pathways of hexenes

摘要

The current work presents new experimental autoignition and speciation data on the two cis-hexenes isomers (cis-2-hexene and cis-3-hexene). The new data together with previous data on the trans-hexene isomers describe the effect of the location of the carbon-carbon double bond and stereoisomeric structures on the reaction pathways of the linear isomers. Experiments were conducted with the University of Michigan rapid compression facility to determine ignition delay times from pressure histories. Stoichiometric (Φ = 1.0) mixtures at dilution levels of buffer gas:O_2 = 7.5 (mole basis) were investigated at an average pressure of 11 atm and temperatures from 803 to 1052 K. The ignition delay time showed negligible sensitivity to the location of the carbon-carbon double bond and the stereoisomeric structure (cis-trans) for the conditions considered, consistent with expectations for alkenes at high temperatures (> 900 K). Model predictions using the Lawrence Livermore National Laboratory reaction mechanism (developed for gasoline surrogate combustion, which includes hexene reaction pathways) for ignition delay times and intermediate species were in generally good agreement with the experimental data. However, the mechanism for 3-hexene significantly over-predicted the formation of small aldehyde (C_2-C_4) species for both stereoisomers.