Oxymethylene dimethyl ethers (CH3O(CH2O)xCH3 or OMEx) are synthetic substitutes of diesel and jet fuel. They can achieve soot-less combustion and have been shown to exhibit favourable ignition characteristics. With the aim to explore their combustion physics, the structure of their flames is analysed using the algorithmic tools of the Computational Singular Perturbation (CSP) method. It is demonstrated that the flame structure and the mechanism for its propagation is encapsulated in the fastest explosive mode, introduced by chemical dynamics in a narrow region of the flame front. This narrow region extends around the point where the maximum heat release rate (MHRR) is recorded. CSP diagnostics identify (i) reactions H + O2→ O + OH and CO + OH → CO2 + H beyond MHRR as initiating an upstream diffusion of heat and H radicals, both of which are generated by the exothermic reaction H2 + OH → H2O + H, (ii) a downstream convective motion that ensues and (iii) chemical activity that is initiated ahead of MHRR and sustained by the convective transport of fuel and oxygen. CSP also identifies differences in the action of the upstream diffusion of heat and H radicals and of the downstream transport of fuel and oxidiser. It is also shown that the fastest explosive mode far from the neighbourhood of MHRR has no influence on the structure and propagation of the flame front. Although OME2−4/air mixtures exhibit drastically different dynamics in the context of homogeneous autoignition, very small differences are recorded in terms of flame structure and propagation. The findings suggests that, since practically all major processes driving the flame front propagation are similar to those of hydrocarbons, OMEx fuels can be used as “drop-in” fuels in currently employed burners.

中文翻译：

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OME[公式省略]/空气混合物：它们的层流预混火焰的结构和传播机制


氧亚甲基二甲醚（CH3O（CH2O）xCH3 或 OMEx）是柴油和喷气燃料的合成替代品。它们可以实现无烟尘燃烧，并已被证明具有良好的点火特性。为了探索它们的燃烧物理学，使用计算奇异扰动 （CSP） 方法的算法工具分析了它们的火焰结构。结果表明，火焰结构及其传播机制被封装在最快的爆炸模式中，该模式由化学动力学在火焰前缘的狭窄区域引入。这个狭窄的区域延伸到记录最大热释放率 （MHRR） 的点周围。CSP 诊断确定 （i） 反应 H + O2→ O + OH 和 CO + OH → MHRR 以外的 CO2 + H 引发热和 H 自由基的上游扩散，这两者都是由放热反应 H2 + OH → H2O + H 产生的，（ii） 随之而来的下游对流运动，以及 （iii） 在 MHRR 之前启动并由燃料和氧气的对流传输维持的化学活动。CSP 还确定了热量和 H 自由基的上游扩散作用以及燃料和氧化剂的下游运输作用的差异。研究还表明，远离 MHRR 附近的最快爆炸模式对火焰前沿的结构和传播没有影响。尽管 OME2−4/空气混合物在均匀自燃的情况下表现出截然不同的动力学，但在火焰结构和传播方面记录的差异非常小。研究结果表明，由于几乎所有驱动火焰前沿传播的主要过程都与碳氢化合物相似，因此 OMEx 燃料可以用作当前使用的燃烧器中的“即用型”燃料。