Low temperature ignition delay times measurements of 1,3,5-trimethylbenzene by rapid compression machine

Abstract

Due to the increased interest on understanding the combustion chemistry of the larger alkyl aromatic as jet fuel surrogate component, we provide new ignition delay time data of 1,3,5-trimethylbenzene/O2/Ar mixtures, for the temperature range between 880 and 1090 K, at the pressure of 20.0 and 30.0 bar and for different mixture equivalence ratio and fuel concentration, by using a well validated rapid compression machine with heating system. Measurements show that no negative temperature coefficient behavior was observed for this fuel. Subsequently, these low temperature ignition delay time data were used to validate several kinetic mechanisms including those of Gudiyella and Brezinsky (Combust Flame 2012), Diévart et al. (Fuel 2013), and Wang et al. (Combust Flame 2018), all of which significantly overestimate the reactivity of 1,3,5-trimethylbenzene in this temperature range. Sensitivity analysis at typical condition and comparisons of the rate constants of the ignition dominant reactions in different models indicate that a more complete reaction scheme for 1,3,5-trimethylbenzene (T135MB) and more accurate rate constant should be further pursued, especially for the reactions of H abstraction from T135MB and fuel radical consumption reactions. Finally, ignition delay times of toluene is lower than T135MB and n-propylbenzene at the same condition, which indicate that the larger number of side chain and the longer side chain length enhances the low temperature reactivity. In addition, for the same fuel isomer, the effect of the side chain length is stronger than the number of side methyl in accelerating ignition since n-propylbenzene presents an even shorter ignition delay times than T135MB. We believe the present work will be of merit for future jet fuel surrogate model development.