Compact Chemical Mechanism for Autoignition and Combustion of Methylcyclohexane under Engine Relevant Conditions

A compact
chemical kinetic mechanism for autoignition and combustion
of methylcyclohexane (MCH) was developed and validated for a wide
range of conditions, especially for low temperatures and high pressures
that are most relevant to real engines. The mechanism was constructed
in steps. An improved C5-C7 submechanism (26
species and 90 reactions) was first developed to describe fuel-cracking
to form smaller fragments under high temperatures. Five modules of
the C5-C7 submechanism were considered separately,
and the rate constants were carefully estimated. A semiglobal low-temperature
submechanism was developed to improve prediction of the negative temperature
coefficient behaviors, which contained 4 species and 11 reactions.
Isomers of intermediate radicals and fast reactions were lumped to
obtain the minimal low-temperature submechanism. Combined with a simplified
C0-C4 kernel (40 species and 276 reactions),
the final mechanism consists of 70 species and 377 reactions. Validations
of the newly developed mechanism were performed using amounts of experimental
data, including ignition delays in shock tubes and rapid compression
machines, under a wide range of temperatures (650–2000 K),
pressures (1–50 atm), and equivalence ratios (0.5–2.0),
and OH concentration histories in high pressure shock tubes. Furthermore,
experimental data of species concentrations and flame speeds in laminar
premixed flames were also used for validation. The present mechanism
showed good accuracy in predicting ignition and combustion properties
over a range of parameters. Simulations using other detailed MCH mechanisms
were also carried out for comparison.