In order to obtain physical insights on ammonia combustion, which is characterised by exceptionally long ignition delays and increased NOx emissions, the autoignition dynamics of an ammonia/air mixture is analysed using the diagnostics tools derived from the Computational Singular Perturbation (CSP) methodology. The results are compared to the autoignition dynamics of a methane/air mixture of same initial conditions. Methane was chosen for comparison because, even though the two molecules have a formal similarity, the ignition delay of methane is more than 10 times shorter than the one of ammonia. By using the CSP diagnostics tools, we identified the dominant chemical pathways that relate to the explosive components that drive the system towards ignition for both cases. Furthermore, the reactions that hinder the ammonia ignition were identified. This led to the determination of an interesting difference in the electronic configuration of the molecules of the two fuels, which is the root of their drastically different oxidation dynamics. In particular, it was shown that the autoignition process starts with the formation of methyl (CH${}_3$) and amine (NH${}_2$) radicals, through dehydrogenation of methane and ammonia, respectively. In the methane case, the methyl-peroxy radical (CH${}_3$–O–O–) then forms, which initiates a chemical runaway that lasts for approximately 2/3 of the ignition delay and leads to the gradual oxidation of carbon to CO${}_2$. In the ammonia case, though, the structure of NH${}_2$ is such that it is not possible to form NH${}_2$–O–O–. As a result, the chemical runaway is suspended.

为了获得氨燃烧的物理洞察力，氨燃烧的特点是点火延迟过长和氮氧化物排放增加，使用源自计算奇异扰动 (CSP) 方法的诊断工具分析氨/空气混合物的自燃动力学。将结果与相同初始条件下甲烷/空气混合物的自燃动力学进行比较。选择甲烷进行比较是因为，尽管这两种分子在形式上有相似之处，但甲烷的点火延迟比氨的点火延迟时间短 10 倍以上。通过使用 CSP 诊断工具，我们确定了与爆炸成分相关的主要化学途径，在这两种情况下，这些成分推动系统着火。此外，还确定了阻碍氨点燃的反应。这导致确定了两种燃料分子电子构型的有趣差异，这是它们氧化动力学截然不同的根源。特别是，表明自燃过程始于甲基（CH${}_3$) 和胺 (NH${}_2$) 自由基，分别通过甲烷和氨的脱氢。在甲烷的情况下，甲基过氧自由基（CH${}_3$–O–O–) 然后形成，这会引发化学失控，持续大约 2/3 的点火延迟，并导致碳逐渐氧化成 CO${}_2$. 然而，在氨的情况下，NH 的结构${}_2$ 是不可能形成NH的${}_2$–O–O–。结果，化学品失控被暂停。