Nitric oxide pollutant formation in high hydrogen content (HHC) syngas flames
Nitric oxide pollutant formation in high hydrogen content (HHC) syngas flames
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DOI：
10.1016/j.ijhydene.2015.08.068
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发表时间：
2015-10
影响因子：
7.2
通讯作者：
K. Dinesh;J. A. Oijen;K. Luo;Xi Jiang
中科院分区：
文献类型：
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作者：
K. Dinesh;J. A. Oijen;K. Luo;Xi Jiang
对雷诺数Re=6000的高氢合成气非预混喷流火焰进行了三维直接数值模拟，研究了NO污染物的生成。所使用的详细化学是GRI 3.0，更新了使用火焰面生成流形(FGM)的NCN自由基化学的影响。通过FGM列表和反应进程变量输运方程考虑了优先扩散效应，基于DNS的定量结果表明，纯氢火焰的火焰温度与NO浓度之间存在很强的相关性，其中NO的生成主要符合Zeldovich机理。结果还表明，由于CO稀释成H2的温度较低，H2/CO合成气中的最大NO值迅速下降。对H2/CO合成气火焰中NO生成途径的研究结果表明，在低应变率下NO的生成主要是由Zeldovich机理决定的，而在高应变率下NO的高生成率完全是由NNH机理引起的。我们还发现，由于CO氧化过程中没有CH自由基，Fenimore机理对H2/CO合成气火焰中NO生成的贡献最小。研究发现，由于优先扩散，火焰底部附近的NO浓度随H2/CO合成气混合气中氢含量的不同而表现出较高的值。
Three-dimensional direct numerical simulations (DNS) of high hydrogen content (HHC) syngas nonpremixed jet flames with a Reynolds number of Re = 6000 have been carried out to study the nitric oxide (NO) pollutant formation. The detailed chemistry employed is the GRI 3.0 updated with the influence of the NCN radical chemistry using flamelet generated manifolds (FGM). Preferential diffusion effects have been considered via FGM tabulation and the reaction progress variable transport equation.The DNS based quantitative results indicate a strong correlation between the flame temperature and NO concentration for the pure hydrogen flame, in which NO formation is mainly characterised by the Zeldovich mechanism. The results also indicate a rapid decrease of maximum NO values in H2/CO syngas mixtures due to lower temperatures associated with the CO-dilution into H2. Results on NO formation routes in H2/CO syngas flames show that while the Zeldovich mechanism dominates the NO formation at low strain rates, the high NO formation rate at high strain rates is entirely caused by the NNH mechanism. We also found that the Fenimore mechanism has a least contribution on NO formation in H2/CO syngas flames due to absence of CH radicals in the oxidation of CO. It is found that, due to preferential diffusion, NO concentration exhibits higher values near the flame base depending on the hydrogen content in H2/CO syngas fuel mixture.