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首页> 外文期刊>Fuel >Optimization of the Eddy Dissipation Concept (EDC) model for turbulence-chemistry interactions under hot diluted combustion of CH4/H-2
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Optimization of the Eddy Dissipation Concept (EDC) model for turbulence-chemistry interactions under hot diluted combustion of CH4/H-2

机译：CH4 / H-2热稀释燃烧下湍流-化学相互作用的涡耗散模型（EDC）模型的优化

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Moderate or Intense Low-oxygen Dilution (MILD) combustion which known as a combustion under highly preheated and diluted condition is a relatively new combustion regime including many differences in comparison with the traditional one. Among many distinguished disparities between combustion modeling of conventional and MILD ones, turbulent-chemistry interaction modeling is an open field of study. Current knowledge on modeling this combustion regime shows that the eddy dissipation concept (EDC) model could be successfully used for modeling of this combustion regime. In this paper, it has been tried to propose some guidelines to modify the semi-empirical constants of the original EDC model for MILD combustion. In this way a parametric study of the EDC model constants for a nonpremixed MILD burner is done in terms of accuracy of prediction while the responses of the model to its constants are focused on the basis of physical arguments. Burner of Dally et al. (JHC) is modeled using the RANS approach in a 2D axisymmetric computational domain for different oxygen levels and fuel jet Reynolds numbers when a reduced detail chemical mechanism of DRM-22 is used to represent the chemical mechanism. Moreover using a well-stirred-reactor analysis and extracting the chemical reactions pathways, discussions are completed. Results show that reducing the CD2 constant which leads to a decrease in time scale and volume fraction constants of the model would improve the performance of the model for MILD condition. Prediction of flame lift-off and minor OH species has been improved by changing default model constants of C-tau and C-gamma to around 0.0893 and 1.0, respectively, especially for lower oxygen levels. Indeed reaction pathway analysis and dimension of reaction zone showed that reducing scales of the defined reactor in the EDC model (i.e. fine structure) to the Kolmogrov or smaller scales might push the reactions inside each structure toward the non-equilibrium condition and enlargement of overall reaction zone and make the EDC model more compatible with MILD combustion characteristics. Reduction in the length and time scales of the fine structure led to improvement in Temperature, OH, and CO profiles inside of MILD region of the JHC burner, although for CO, disagreement is still considerable. Considering error analysis of five checked parameters (i.e. H2O, CO2, OH, CO, and temperature) at both MILD and conventional regions of the JHC burner may conduct us toward that the defaults setting of the model still works reasonably on the whole when it is used at both regions. (C) 2016 Elsevier Ltd. All rights reserved.
机译：中度或强烈的低氧稀释（MILD）燃烧，即在高度预热和稀释的条件下燃烧，是一种相对较新的燃烧方式，与传统燃烧方式相比，存在许多差异。在常规燃烧模型和MILD燃烧模型之间的许多显着差异中，湍流-化学相互作用模型是一个开放的研究领域。目前对这种燃烧状态进行建模的知识表明，涡耗概念（EDC）模型可以成功地用于该燃烧状态的建模。在本文中，已尝试提出一些准则来修改MILD燃烧的原始EDC模型的半经验常数。这样，就可以根据预测的准确性对非预混合MILD燃烧器的EDC模型常数进行参数研究，而模型对其常数的响应则基于物理参数。 Dally等人的燃烧器。 （JHC）是使用RANS方法在2D轴对称计算域中对不同的氧气含量和燃料射流雷诺数建模的，其中使用了DRM-22的简化细节化学机理来表示该化学机理。此外，使用充分搅拌的反应器分析并提取化学反应路径，从而完成了讨论。结果表明，减小CD2常数会导致模型的时间尺度和体积分数常数减小，这将改善模型在MILD条件下的性能。通过将C-tau和C-γ的默认模型常数分别更改为约0.0893和1.0，尤其是对于较低的氧气含量，改进了火焰剥离和少量OH种类的预测。确实，反应路径分析和反应区尺寸表明，将EDC模型中定义的反应器的规模（即精细结构）减小到Kolmogrov或更小规模，可能会将每个结构内的反应推向非平衡状态，并扩大整体反应区域，使EDC模型与MILD燃烧特性更加兼容。精细结构的长度和时间尺度的减少导致JHC燃烧器的MILD区域内部的温度，OH和CO分布的改善，尽管对于CO而言，分歧仍然很大。考虑到JHC燃烧器的MILD和常规区域的五个检查参数（即H2O，CO2，OH，CO和温度）的误差分析，可能会使我们朝着模型的默认设置在总体上仍然合理地起作用的方向进行分析。在两个地区都使用。 （C）2016 Elsevier Ltd.保留所有权利。

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