Ignition delay times measurement and kinetic modeling studies of 1-heptene, 2-heptene and n-heptane at low to intermediate temperatures by using a rapid compression machine

In this work, we have firstly investigated the auto-ignition behaviors of 1-heptene, 2-heptene and n-heptane in the low to intermediate temperature range (650-950 K) over various equivalence ratios at 15 and 23 bar using a rapid compression machine. Results show that n-heptane exhibits the expected negative temperature coefficient (NTC) behavior and shows the shortest IDTs among the three fuels, while the NTC behavior for 1-heptene and 2-heptene is moderated and quasi-Arrhenius temperature dependence of the 1st stage IDTs is observed at all test conditions. As the temperature increased over 900 K, the IDTs of the three fuels begin to be consistent indicating a moderated effect of the unsaturated bond. In the NTC temperature region, 1-heptene shows higher reactivity than 2-heptene, while opposite relative reactivity is observed in the temperature beyond the NTC region. The IDT data of 1-heptene, 2-heptene and n-heptane were then used to validate several kinetic models. Results show that the performance of the n-heptane models is generally good, while all the models underestimate the low temperature reactivity of 1-heptene. Finally, a model refinement has been made and the prediction shows better agreement with the present measured IDT as well as the experimental pressure evolution trace in literature.