Effects of infinitely fast chemistry on combustion behavior of coaxial diffusion flame predicted by large eddy simulation
Effects of infinitely fast chemistry on combustion behavior of coaxial diffusion flame predicted by large eddy simulation
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DOI：
10.1016/j.fuproc.2019.106226
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发表时间：
2020-03
影响因子：
7.5
通讯作者：
Shota Akaotsu;Ryoma Ozawa;Y. Matsushita;H. Aoki;W. Malalasekera
中科院分区：
文献类型：
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作者：
Shota Akaotsu;Ryoma Ozawa;Y. Matsushita;H. Aoki;W. Malalasekera
基于湍流燃烧模型的大涡模拟有助于燃烧器的设计和优化。在现有的各种燃烧模型中，涡流分解（EBU）模型被广泛使用，因为它假设了无限快的化学反应。然而，忽略实际的化学动力学会导致意想不到的行为，并且需要阐明燃烧模型的特征。本文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，但在燃料和氧化剂流混合区域的燃烧产物的气体温度和质量分数被高估了。相比之下，火焰/进程变量（FPV）模型得出的结果与实验数据更吻合，因为EBU模型假设了无限快的化学反应，而FPV模型中使用的查找表是基于实际的化学动力学。由于这些模型可以用于煤和喷雾燃烧的CFD模拟，因此本研究的结果对于有效地模拟实际燃烧系统应该是有用的。
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.