Ammonia (NH) has gained increasing recognition as a carbon-free fuel. To enhance NH combustion, reactive gases, like methane (CH), are usually added to the combustion system. In this work, the role of CH in NH combustion is systematically studied. A series of reactive force field molecular dynamic (ReaxFF MD) simulations are implemented to investigate effects of CH addition on the consumption of NH and the yields of nitrogen oxides (NO) from the atomic perspective: CH accelerates the consumption of NH by shortening the decomposition time of the first NH molecule and increasing the translational kinetic energy of the system; CH modifies the yield of NO by complicating the elementary reactions and introducing additional intermediates. The fuel ratio of CH and NH between 0.5 and 1 is suggested for a cleaner and enhanced NH combustion. By summarising the findings from the latest publications and the present work, the role of CH in NH combustion is comprehensively analysed from the macroscale and microscale perspectives: CH accelerates the progress of NH combustion flame, activates chemical reactions, and aggravates NO emissions at a low CH content. Taking the NH/CH combustion as an example, this study provides an exclusive perspective to understand combustion phenomena from the microscale events to macroscale observations.

中文翻译：

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甲烷在空气中氨燃烧中的作用：从微观到宏观

氨 (NH) 作为一种无碳燃料已得到越来越多的认可。为了增强 NH 的燃烧，通常会在燃烧系统中添加活性气体，例如甲烷 (CH)。在这项工作中，系统地研究了 CH 在 NH 燃烧中的作用。通过一系列反应力场分子动力学 (ReaxFF MD) 模拟，从原子角度研究 CH 添加对 NH 消耗和氮氧化物 (NO) 产量的影响：CH 通过缩短分解来加速 NH 的消耗第一个 NH 分子的时间并增加系统的平动动能； CH 通过使基元反应复杂化并引入额外的中间体来改变 NO 的产率。建议 CH 和 NH 的燃料比例在 0.5 到 1 之间，以实现更清洁和增强的 NH 燃烧。通过总结最新出版物和当前工作的研究结果，从宏观和微观角度全面分析了CH在NH燃烧中的作用：CH加速了NH燃烧火焰的进展，激活了化学反应，并在较低的条件下加剧了NO排放CH含量。以NH/CH燃烧为例，本研究为理解从微观事件到宏观观察的燃烧现象提供了独特的视角。