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Optimized chemistry for Large Eddy Simulations of wrinkled flames
Proceedings of the Combustion Institute ( IF 3.4 ) Pub Date : 2020-10-14 , DOI: 10.1016/j.proci.2020.09.028
C. Mehl , M. Cailler , R. Mercier , V. Moureau , B. Fiorina

State-of-the-art LES models have made significant progress in the prediction of heat release and flame propagation for a wide range of combustion regimes. Predicting pollutants remains however a difficult issue, especially in situations where sub-grid scale wrinkling is high. A novel strategy, named COPLES (Chemistry OPtimized for LES), is presented in this paper to account for the effect of sub-grid scale wrinkling on pollutants formation in a transported chemistry context and under flamelet regime assumption. New chemical mechanisms are built through an optimization process to recover the properties of filtered flames. Two alternative formulations are proposed. The first one consists in optimizing the COPLES parameters to retrieve the structure of Filtered Planar Flame (FPF) and to include separately the impact of sub-grid scale wrinkling. The second formulation targets directly a collection of Filtered Wrinkled Flamelets (FWF), so that the influence of turbulence on the chemical flame structure is intrinsically accounted for. The two approaches are successfully validated on 1-D freely propagating premixed flames and then challenged against the standard Thickened Flame for LES model on a turbulent premixed swirled combustor, experimented at Cambridge University. Whereas all formulations retrieve the temperature field, the COPLES-FWF model improves significantly the prediction of CO formation.



中文翻译:

用于大涡旋模拟的优化化学结构

最先进的LES模型在各种燃烧方案的热量释放和火焰传播的预测中取得了重大进展。然而,预测污染物仍然是一个难题,特别是在次网格规模起皱较大的情况下。本文提出了一种名为COPLES(针对LES进行化学优化的化学方法)的新策略,以说明在运输化学环境中以及在小火焰状态下,亚网格尺度起皱对污染物形成的影响。通过优化过程可以建立新的化学机制,以恢复过滤后火焰的特性。提出了两种替代方案。第一个步骤是优化COPLES参数,以检索过滤平面火焰(FPF)的结构,并单独包括子网格水垢起皱的影响。第二种配方直接针对过滤皱纹小火焰(FWF)的集合,这样就可以从根本上解决湍流对化学火焰结构的影响。两种方法均在自由传播的一维自由预混火焰上得到成功验证,然后在剑桥大学实验的湍流预混涡流燃烧器上针对LES模型的标准“加厚火焰”提出了挑战。尽管所有配方都可以检索温度场,但是COPLES-FWF模型可以显着改善对CO形成的预测。两种方法均在自由传播的一维自由预混火焰上得到成功验证,然后在剑桥大学实验的湍流预混涡流燃烧器上针对LES模型的标准“加厚火焰”提出了挑战。尽管所有公式都可以检索温度场,但COPLES-FWF模型可以显着改善对CO形成的预测。两种方法均在自由传播的一维自由预混火焰上得到成功验证,然后在剑桥大学实验的湍流预混涡流燃烧器上针对LES模型的标准“加厚火焰”提出了挑战。尽管所有配方都可以检索温度场,但是COPLES-FWF模型可以显着改善对CO形成的预测。

更新日期:2020-10-15
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