Comparative studies on the ignition characteristics of diisobutylene isomers and iso-octane by using a rapid compression machine

In this work, we have compared the auto-ignition behaviors of 2,4,4-trimethyl-1-pentene (DIB-1) and 2,4,4-trimethyl-2-pentene (DIB-2), and iso-octane in the low to intermediate temperature range (660-950 K) over various equivalence ratios at 20 and 30 bar using a rapid compression machine. Results show that iso-octane exhibits the expected negative temperature coefficient (NTC) behavior and the highest reactivity (lowest ignition delay times, IDTs) in the low temperature region. Both DIB-1 and DIB-2 show less low-temperature reactivities and quasi-Arrhenius temperature dependence of the IDTs were observed at all test conditions. Due to the similarity of the molecular structure of DIB-1, DIB-2 and iso-octane, the effects of the unsaturated bond and its position are assessed and compared with that for linear alkenes. The IDT data of DIB-1, DIB-2 and iso-octane were then used to validate several recently developed kinetic models. Results show that the performances of the iso-octane models are generally good, while model performance for predictions of IDTs for DIB needs to be improved especially at low temperatures. Finally, kinetic analyses explained the reactivity difference caused by double bond and its position, based on which further model optimization suggestions are proposed.