An experimental and chemical kinetic modeling study of octane isomer oxidation. Part 2: 223- and 224-trimethylpentane

In this work, a detailed chemical kinetic model is developed to describe the oxidation of 2,2,3-trimethyl pentane (223-TMP) using NUIGMech1.3 as the core mechanism. Moreover, the kinetics of iso-octane are also updated based on our latest rate rules. The thermodynamic properties of the fuels (RH), alkyl (Ṙ), alkyl peroxy (RȮ₂), hydroperoxy-alkyl (Q˙OOH) and peroxy hydroperoxy alkyl (Ȯ₂QOOH) radicals that form part of the 223- and 224-TMP sub-mechanisms are determined either using group additivity values derived from high-level CCSD(T)-F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ quantum chemistry calculations or directly from these quantum chemistry calculations. The rate constants of the key reactions in the 223- and 224-TMP sub-mechanisms are determined based on a review of relevant theoretical studies. Moreover, ignition delay time measurements using both a high-pressure shock tube and a rapid compression machine are newly measured for both isomers over a wide range of temperatures (600–1470 K), at pressures of 15 atm and 30 atm, and at equivalence ratios of 0.5, 1.0 and 2.0 in ‘air’. The kinetic models developed for both fuels are validated against the present ignition delay time data and literature data where available, and the model is in general good agreement with the experimental measurements. The ignition delay times of 223- and 224-TMP are also compared to 234-TMP and the reactivity is in the order 224-TMP > 234-TMP > 223-TMP which is consistent with their octane numbers of 100, 102.9 and 109.6, respectively.