Investigation of the low-temperature cyclohexane oxidation

The existence or non-existence of the negative temperature coefficient (NTC) region in cyclo-hexane (cyC6H12) oxidation is still an open question in the literature. This paper addresses this issue by presenting the rapid compression machine (RCM) and shock tube (ST) data and a consistent model to predict ignition delay times in agreement with experimental data. To this end, a semi-detailed chemical kinetic mechanism has been updated and improved to study the cyclohexane combustion at both low- and high-temperatures including polyromantic molecule (PAH) formation. The reaction mechanism is based on the 20 reaction classes; two of those were newly included in the model: cyclohexenyl peroxy formation and isomerization of hydroperoxy peroxy radical. For the main reaction classes, uncertainty boundaries of the rate coefficients have been evaluated. The NTC behavior observed in the RCM experiments was not detected in the ST measurements and in simulations performed with the developed model. The simulations performed with other literature models revealed that reaction models, which described the NTC region fixed in the RCM experiments, were unable to reproduce accurately the shock tube data. It is shown, that the cyC6H12 oxidation chemistry is controlled by competition between three main reaction pathways over the full temperature interval. The developed model describes successfully laminar flame speed data and species profiles from burner-stabilized premixed flames.