Experimental and modeling study of the autoignition of 1-hexene/isooctane mixtures at low temperatures

Autoignition delay times have been measured in a rapid compression machine at Lille at temperatures after compression from 630 to 840 K, pressures from 8 to 14 bar, Φ=1Φ=1, and for a isooctane/1-hexene mixture containing 82% isooctane and 18% 1-hexene. Results have shown that this mixture is strongly more reactive than pure isooctane, but less reactive than pure 1-hexene. It exhibits a classical low-temperature behavior, with the appearance of a cool flame and a negative temperature coefficient region. The composition of the reactive mixture obtained after the cool flame has also been determined. A detailed kinetic model has been obtained by using the system EXGAS, developed in Nancy for the automatic generation of kinetic mechanisms, and an acceptable agreement with the experimental results has been obtained both for autoignition delay times and for the distribution of products. A flow-rate analysis reveals that the cross-reactions between species coming from both reactants (like H abstractions or combinations) are negligible in the main flow consumption of the studied hydrocarbons. The ways of formation of the main primary products observed and the most sensitive rate constants have been identified.