This study investigated the effect of the H fraction on reaction dynamics and NO formation in a premixed NH/H/air jet flame within a hot coflow (JHC) through numerical simulations. We found that even a small mole fraction of H (e.g., = 5%) significantly enhances the ignition of the premixed NH/air flame. However, the presence of H markedly intensifies the main combustion reactions only when ≥ 30%, resulting in a sharp increase in temperature and heat release rate. Moreover, as increases, the NO emission first increases until = 75% and then decreases. Without any H addition, a high emission of unburned NH occurs in the pure NH JHC flame. On the other hand, when ≥ 50%, the emissions of unburned H and OH increase rapidly due to extremely high temperatures. Notably, maintaining between 5% and 20% minimizes the emissions of NO, NH, H, and OH. Furthermore, the preferential diffusion of H plays a key role in enhancing the production of active radicals (OH, O, and H), thereby significantly boosting the initiation and combustion reactions of NH/H blended fuel.

中文翻译：

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H2 比例对热低氧气流中 NH3/H2/空气燃烧的影响

本研究通过数值模拟研究了热协流 (JHC) 内预混合 NH/H/空气喷射火焰中 H 分数对反应动力学和 NO 形成的影响。我们发现，即使 H 摩尔分数很小（例如 = 5%），也能显着增强预混合 NH/空气火焰的点燃。然而，只有当H含量≥30%时，H的存在才会显着加剧主要燃烧反应，导致温度和放热率急剧上升。而且，随着增加，NO排放量首先增加直至= 75%，然后减少。在不添加任何 H 的情况下，纯 NH JHC 火焰中会大量排放未燃烧的 NH。另一方面，当≥50%时，由于极高的温度，未燃烧的H和OH的排放量迅速增加。值得注意的是，保持在 5% 到 20% 之间可以最大限度地减少 NO、NH、H 和 OH 的排放。此外，H的优先扩散在增强活性自由基（OH、O和H）的产生方面起着关键作用，从而显着促进NH/H混合燃料的引发和燃烧反应。