1,2,4-trimethylbenzene is an important representative aromatic component of gasoline/diesel/jet fuels and thus it is necessary to understand its low-temperature chemistry. In this paper, ignition delay times (IDTs) of both 1,2,4-trimethylbenzene (124TMB) and its blends with n-heptane were measured at engine-like conditions using both a high-pressure shock tube and a rapid compression machine for fuel in ‘air’ mixtures at pressures of 10 and 30 atm and at temperatures in the range 600 – 1100 K. The experiments in this study show for the first time that 124TMB presents a two-stage ignition behavior at engine relevant conditions. Blending n-heptane with 124TMB can significantly increase mixture reactivity at temperatures below 1000 K. A new detailed mechanism has been developed to simulate the experimentally measured IDT data. The mechanism can capture well the two-stage ignition behavior as well as the ignition delays at different pressures, equivalence ratios over a wide temperature range, for both pure fuels and their blended mixtures. Flux analyses show that the benzylic radicals (formed via H-atom abstraction from the methyl groups ortho-sites on 124TMB) can add to O₂ forming RȮ₂ radicals, which can isomerize to $\dot{\mathrm{Q}}$OOH by intramolecular H-atom transfer from the ortho- methyl group and these $\dot{\mathrm{Q}}$OOH radicals undergo a second addition to O₂. This is analogous to the chain branching reaction pathways of alkanes. The chain branching reaction pathways are responsible for the first-stage heat release of 124TMB. The competitions between chain branching and both chain propagating and chain termination reaction pathways lead to a less pronounced negative temperature coefficient (NTC) behavior for 124TMB oxidation, compared to two-stage ignition behavior observed for alkanes and other fuels.

1,2,4-三甲基苯是汽油/柴油/喷气燃料中重要的代表性芳烃组分，因此有必要了解其低温化学性质。在本文中，使用高压激波管和快速压缩机在类似发动机的条件下测量了1,2,4-三甲基苯 (124TMB) 及其与正庚烷的混合物的点火延迟时间 (IDT) “空气”混合物中的燃料在 10 和 30 atm 的压力和 600 – 1100 K 的温度范围内。本研究中的实验首次表明 124TMB 在发动机相关条件下呈现两阶段点火行为。混合n-具有 124TMB 的庚烷可以在低于 1000 K 的温度下显着提高混合物的反应性。已经开发出一种新的详细机制来模拟实验测量的 IDT 数据。该机制可以很好地捕捉纯燃料及其混合混合物在不同压力、宽温度范围内的当量比下的两阶段点火行为以及点火延迟。通量分析表明，苄基自由基（通过从 124TMB 上的甲基邻位位点提取 H 原子形成）可以加到 O ₂上形成 Rş ₂自由基，后者可以异构化为$\dot{\mathrm{问}}$OOH 通过分子内氢原子从邻甲基转移而来$\dot{\mathrm{问}}$OOH 自由基经历第二次加成到 O2_中。这类似于烷烃的链支化反应途径。链支化反应途径负责 124TMB 的第一阶段放热。与烷烃和其他燃料观察到的两阶段点火行为相比，链支化与链增长和链终止反应途径之间的竞争导致 124TMB 氧化的负温度系数 (NTC) 行为不太明显。