The hydrogen carrier ammonia is considered a prominent carbon-free alternative fuel. This paper examines the impact of flue gas recirculation (FR) on combustion instability and emission behavior of premixed CH/NH/air swirl flame at different equivalence ratios (Φ) and ammonia mole fractions (). Experimental results show that FR is beneficial to suppressing the self-excited pulsating pressure and pulsating heat release rate of CH/NH/air flame, and the pulsating frequency decreases monotonically with the increase of FR. Under fuel-lean and stoichiometric conditions, FR is beneficial to suppressing NOx formation but will increase CO and NH emissions. Under fuel-rich conditions, FR reduces CO emissions but increases NOx emissions. The NO emissions obtained from the chemical reactor network simulation are in qualitative agreement with the experimental results. The results show that the elementary reactions related to HNO and NHi radicals play a crucial role in the influence of FR on NO formation.

中文翻译：

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烟气再循环对预混CH4/NH3/空气火焰燃烧不稳定性及排放特性的影响

氢载体氨被认为是一种著名的无碳替代燃料。本文研究了烟气再循环（FR）对不同当量比（Φ）和氨摩尔分数（）下预混CH/NH/空气旋流火焰的燃烧不稳定性和排放行为的影响。实验结果表明，FR有利于抑制CH/NH/空气火焰的自激脉动压力和脉动放热速率，且脉动频率随着FR的增加而单调下降。在贫油和化学计量条件下，FR 有利于抑制 NOx 的形成，但会增加 CO 和 NH 的排放。在燃料丰富的条件下，FR 可减少 CO 排放，但会增加 NOx 排放。化学反应器网络模拟得到的NO排放量与实验结果定性一致。结果表明，与HNO和NHi自由基相关的基元反应在FR对NO形成的影响中起着至关重要的作用。