Abstract Autoignition characteristics of methane/diesel mixtures with diesel fractions of 5%, 15%, and 30% were investigated in a heated shock tube over temperatures of 960–1500 K, pressures of 6–20 bar, and equivalence ratios of 0.5, 1.0 and 2.0. Generally, ignition delay times (IDTs) decrease with increasing reflected-shock pressure or diesel content. The total equivalence ratio exhibits a slight influence on IDTs, whereas a crossover for IDTs occurs at a higher temperature from fuel-lean to fuel-rich conditions. Besides, three mechanisms in conjunction with a well-validated diesel surrogate were used to predict the IDTs of dual-fuel mixtures. Mech-3 (CRECK-2003) demonstrates the best performance under all test conditions based on quantitative error analysis. Moreover, there is a nonlinear mixing effect for methane/diesel mixtures. The IDT-reducing effect of diesel to methane is more pronounced compared to n-heptane, especially at intermediate-temperatures. Furthermore, the impact of diesel-addition on methane ignition was explored with kinetic analyses including species evolution, brute-force sensitivity analysis and rate of production analysis. These active radicals produced at the initial stage, especially for H radicals rapidly generated through the decomposition of diesel, readily trigger H-abstraction reactions on CH4, resulting in the continuous production of H from HCO decomposition and eventually triggering the hot-ignition via the chain-branching reactions of H + O2 = O + OH and H2 + O = H + OH. Consequently, the main reason for the IDT-reduction by diesel-addition at the high temperature is the rapid decomposition of diesel to produce H during the initial ignition period.

中文翻译：

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少量柴油添加对反射冲击波后甲烷点火的影响：实验和建模

摘要 在 960–1500 K 的温度、6–20 bar 的压力和 0.5、1.0 的当量比下，在加热激波管中研究了柴油比例为 5%、15% 和 30% 的甲烷/柴油混合物的自燃特性和 2.0。通常，点火延迟时间 (IDT) 会随着反射冲击压力或柴油含量的增加而减少。总当量比对 IDT 的影响很小，而 IDT 的交叉发生在从贫燃料到富燃料条件的较高温度下。此外，结合经过充分验证的柴油替代品的三种机制用于预测双燃料混合物的 IDT。Mech-3 (CRECK-2003) 在基于定量误差分析的所有测试条件下展示了最佳性能。此外，甲烷/柴油混合物存在非线性混合效应。与正庚烷相比，柴油对甲烷的 IDT 降低效果更明显，尤其是在中等温度下。此外，通过包括物种演化、蛮力敏感性分析和产率分析在内的动力学分析，探索了添加柴油对甲烷点火的影响。这些在初始阶段产生的活性自由基，特别是柴油分解迅速产生的H自由基，很容易引发CH4上的吸氢反应，导致HCO分解不断产生H，最终通过链引发热点火-H + O2 = O + OH 和 H2 + O = H + OH 的支化反应。最后，