Probing the antiknock effect of anisole through an ignition, speciation and modeling study of its blends with isooctane

Carstensen , Hans-Heinrich
38 th International Symposium on Combustion
Participation type: 
Comunicación oral
Other authors: 
Carolina S. Mergulhão, Hwasup Song, Scott W. Wagnon, William J. Pitz, Guillaume Vanhove
Adelaide, Australia

In order to unravel the reaction pathways relevant to anisole co-oxidation within a fuel blend, a detailed
study of isooctane/anisole blends was performed with the ULille RCM. Ignition delays as well as mole frac-
tion profiles were measured during a two-stage ignition delay using sampling and GC techniques. These re-
sults are used to validate a kinetic model developed from ab initio calculations for the most relevant rate
constants which included H-atom abstraction reactions from anisole, and reactions on the potential energy
surfaces of methoxyphenyl + O 2 and anisyl + O 2 . Pressure dependent rate constants were computed
for the methoxyphenyl + O 2 and anisyl + O 2 reactive systems using master equation code analysis. The new
kinetic model shows good agreement with the experimental data. Dual brute-force sensitivity analysis was
performed, on both first- and second-stages of ignition, allowing the identification of the most important re-
actions in the prediction of both ignition delays. It was observed that while pure anisole does not show NTC
behavior, a 60/40 isooctane/anisole blend displays such behavior, as well as two-stage ignition. This suggests
anisole addition may not be as beneficial to knock resistance as expected from its high octane number. The kinetic
modeling results demonstrate the importance of H-abstraction reactions both from the methoxy group
and from the aryl ring in ortho-position and the addition of the resultant radicals to O 2 , mostly leading to
the formation of polar or non-aromatic products..