Curvature effects on NO formation in wrinkled laminar ammonia/hydrogen/nitrogen-air premixed flames
Curvature effects on NO formation in wrinkled laminar ammonia/hydrogen/nitrogen-air premixed flames
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DOI：
10.1016/j.combustflame.2021.111520
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发表时间：
2021-10
影响因子：
4.4
通讯作者：
Corinna Netzer;Ahfaz Ahmed;A. Gruber;T. Løvås
中科院分区：
文献类型：
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作者：
Corinna Netzer;Ahfaz Ahmed;A. Gruber;T. Løvås
采用二维直接数值模拟（DNS）结合详细化学动力学和一维自由传播火焰计算，研究了NH3/H2/N2-空气预混火焰中NO的生成. NO形成的空间格局被观察到是密切相关的火焰曲率和热扩散作用的关键化学物种的影响。优先扩散的H2到凸形部分的火焰前端导致局部当量比的增加。这种局部当量比的变化被发现显着影响NO的形成。如果燃料-氧化剂混合物是全局贫的，则当量比的局部增加加强了NO的形成（局部地）;相反地，在全局富的燃料-氧化剂混合物中，NO浓度将对应于当量比的局部增量而降低。对NO生成的敏感性分析表明，NH 2的分解受两条竞争途径控制：一方面是通过NH和N分解为N2，另一方面是通过HNO氧化为NO.当地的自由基池，这是受优先扩散的H 2和耗尽的O 2，和当地的燃料-氧化剂的混合比共同加强进一步的局部差异之间的H 2-耗尽（凹状）部分的火焰前锋和H 2-丰富（凸状）的。这在从稀到富的宽范围当量比条件下得到证实。
The formation of nitrogen oxide (NO) in wrinkled laminar NH 3/H 2/N 2-air premixed flames is investigated utilizing two-dimensional Direct Numerical Simulation (DNS) with detailed chemical kinetics as well as one-dimensional freely propagating flame calculations. The spatial pattern of NO formation is observed to be closely linked to flame curvature and affected by thermo-diffusive effects acting on key chemical species. Preferential diffusion of H 2 into convex-shaped portions of the flame front leads to a local increase in equivalence ratio. This change in local equivalence ratio is found to prominently affect the NO formation. If the fuel-oxidant mixture is globally lean, a local increase in equivalence ratio strengthens the NO formation (locally); in a globally rich fuel-oxidant mixture, conversely, the NO concentration will be reduced in correspondence of local increments of the equivalence ratio. A sensitivity analysis with respect to NO formation reveals that decomposition of NH 2 is governed by two competing pathways: the decomposition via NH and N to N 2 on the one hand and the oxidation via HNO to NO on the other hand. The local radical pool, which is affected by preferential diffusion of H 2 and depletion of O 2, and the local fuel-oxidant mixture ratio jointly strengthen further local differences between H 2-depleted (concave-shaped) portions of the flame front and H 2-enriched (convex-shaped) ones. This is confirmed across a wide range of equivalence ratios from lean to rich conditions.