Relative influence of soot oxidation kinetics and subfilter soot-turbulence interactions on soot evolution in turbulent nonpremixed flames
Relative influence of soot oxidation kinetics and subfilter soot-turbulence interactions on soot evolution in turbulent nonpremixed flames
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DOI：
10.1016/j.proci.2022.08.009
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发表时间：
2022-10
影响因子：
3.4
通讯作者：
Pavan Prakash Duvvuri;Hernando Maldonado Colmán;M. Mueller
中科院分区：
文献类型：
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作者：
Pavan Prakash Duvvuri;Hernando Maldonado Colmán;M. Mueller
碳烟的氧化是决定碳烟在湍流反应流中演化的关键过程。一方面，碳烟氧化的动力学速率仍然是碳烟模型中最重要的不确定性之一。另一方面，湍流输送在相对于火焰结构的烟尘分布中起着重要作用，因此烟尘在实际可能发生氧化的区域中的位置。这项工作的目的是评估小尺度湍流传输和氧化动力学的湍流非预混火焰中的碳烟演变的预测的相对重要性。采用一系列碳烟子过滤PDF模型（对碳烟的小尺度湍流输运有不同的假设）和一系列碳烟氧化动力学速率（OH和O2氧化动力学速率不同），对乙烯和空气的湍流非预混射流火焰进行了一系列大涡模拟。与以前的工作类似，结果表明，由于烟尘氧化，在贫混合物中烟尘的消失占是非常重要的，以避免过度的“假氧化”的烟尘，否则人为地存在于贫混合物。此外，碳烟氧化动力学的敏感性被发现是显着不那么重要，比这种效果。然而，一旦这种影响被考虑到在烟尘子过滤器PDF，烟尘氧化动力学的灵敏度变得相当显着相比，进一步细化烟尘子过滤器PDF模型。更具体地说，在烟尘子过滤器PDF模型中的假设，无论烟尘氧化是无限快或有限的速率相比，小规模的湍流传输是一个不太重要的模型灵敏度相比，烟尘氧化的动力学速率的灵敏度。此外，OH和O2的氧化揭示了在碳烟演变中发挥根本不同的作用。
Oxidation of soot is a critical process in determining the evolution of soot in turbulent reacting flows. On the one hand, the kinetic rates of soot oxidation remain one of the most significant uncertainties in soot models. On the other hand, turbulent transport plays a significant role in the distribution of soot with respect to the flame structure so the location of soot in regions where oxidation can actually occur. The objective of this work is to assess the relative importance of small-scale turbulent transport and oxidation kinetics on the prediction of soot evolution in turbulent nonpremixed flames. A series of Large Eddy Simulations has been performed in a turbulent nonpremixed piloted jet flame of ethylene and air using a series of soot subfilter PDF models (with different assumptions regarding the small-scale turbulent transport of soot) and a series of kinetic rates for soot oxidation (with differences in kinetic rates for both OH and O 2 oxidation). Similar to previous work, the results show that accounting for the disappearance of soot in lean mixtures due to soot oxidation is extremely important to avoid excessive “spurious oxidation” of soot otherwise artificially present in lean mixtures. In addition, the sensitivity to soot oxidation kinetics is found to be significantly less important than this effect. However, once this effect is taken into account in the soot subfilter PDF, the sensitivity to soot oxidation kinetics becomes rather significant compared to further refinements to the soot subfilter PDF models. More specifically, the assumption in the soot subfilter PDF models whether soot oxidation is infinitely fast or finite rate compared to small-scale turbulent transport is a less significant model sensitivity compared to the sensitivity to the kinetic rates of soot oxidation. Furthermore, oxidation by OH and O 2 are revealed to play fundamentally different roles in soot evolution.