Large eddy simulations (LES) based on turbulent combustion models aid the design and optimization of combustors. Of the various combustion models available, the eddy break up (EBU) model is widely used because it assumes an infinitely fast chemistry. However, omitting the actual chemical kinetics can cause unexpected behavior, and the characteristics of the combustion models need to be elucidated. Here, the effects of an infinitely fast chemistry on the combustion behavior of a coaxial diffusion flame as predicted by an LES were analyzed. Although the EBU model captured the overall behavior of the chemical species as well as the flow field, the gas temperature and mass fractions of the combustion products in the mixing region of the fuel and oxidizer streams were overestimated. In contrast, the flamelet/progress variable (FPV) model yielded results that were in better agreement with the experimental data, because while the EBU model assumes an infinitely fast chemistry, the look-up tables used in the FPV model are based on the actual chemical kinetics. As these models can be used for the CFD simulations of coal and spray combustion, the results of this study should be useful for efficiently simulating practical combustion systems.

中文翻译：

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大涡模拟预测无限快化学对同轴扩散火焰燃烧行为的影响

基于湍流燃烧模型的大涡模拟 (LES) 有助于燃烧器的设计和优化。在各种可用的燃烧模型中，涡流分解 (EBU) 模型被广泛使用，因为它假定化学过程无限快。然而，忽略实际的化学动力学可能会导致意外行为，需要阐明燃烧模型的特征。在这里，分析了无限快化学对 LES 预测的同轴扩散火焰燃烧行为的影响。尽管 EBU 模型捕获了化学物质的整体行为以及流场，但高估了燃料和氧化剂流混合区域中燃烧产物的气体温度和质量分数。相比之下，火焰/进程变量 (FPV) 模型产生的结果与实验数据更加吻合，因为虽然 EBU 模型假设化学过程无限快，但 FPV 模型中使用的查找表基于实际化学动力学。由于这些模型可用于煤和喷雾燃烧的 CFD 模拟，因此本研究的结果应该有助于有效模拟实际燃烧系统。