A comprehensive study of flamelet tabulation methods for pulverized coal combustion in a turbulent mixing layer—Part II: Strong heat losses and multi-mode combustion
A comprehensive study of flamelet tabulation methods for pulverized coal combustion in a turbulent mixing layer—Part II: Strong heat losses and multi-mode combustion
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DOI：
10.1016/j.combustflame.2019.12.028
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发表时间：
2020-01
影响因子：
4.4
通讯作者：
X. Wen;M. Rieth;A. Scholtissek;O. Stein;Haiou Wang;K. Luo;A. Kronenburg;Jianren Fan;C. Hasse
中科院分区：
文献类型：
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作者：
X. Wen;M. Rieth;A. Scholtissek;O. Stein;Haiou Wang;K. Luo;A. Kronenburg;Jianren Fan;C. Hasse
本文是我们在第一部分中所做工作的延续，其中进行了优先级和预算分析，Wen等人（2019）。在这项工作中，我们的重点是解决具体的和反复出现的问题，在小火焰建模的煤粉燃烧，包括强热损失，多模式燃烧和反应过程变量定义。首先，开发了扩展的小火焰配方，可以考虑到煤粉燃烧系统中强烈的热损失效应。然后，为了表征煤粉火焰的多模式燃烧，利用燃烧模式指数建立了预混和非预混小火焰的耦合模型。最后，量化了反应过程变量定义对小火焰预测的影响。采用最先进的直接数值模拟数据库对新开发的火焰模型进行了挑战。通过优先分析，将表中的热化学量与参考的直接数值模拟结果进行了比较。结果表明，新建立的考虑了强热损失效应的火焰模型能较好地预测气体温度和物质质量分数。绝热小火焰模型在相间传热显著的区域过高预测了相应的热化学量。结合线性外推法，可以改进用绝热小火焰模型预测气体温度的方法。多模式小火焰模型的性能取决于能否正确识别局部燃烧模式。传统的基于燃料和氧化剂种类质量分数梯度的燃烧模式指数不能正确识别整个燃烧场的燃烧模式。
This paper is a continuation of our work done in Part I, in which thea prioriandbudget analyseswere conducted, Wen et al. (2019). In this work, we focus on addressing specific and recurring issues in flamelet modeling for pulverized coal combustion, including strong heat losses, multi-mode combustion and reaction progress variable definition. First, extended flamelet formulations are developed that can take into account strong heat loss effects in pulverized coal combustion systems. Then, to characterize multi-mode combustion in pulverized coal flames, a coupled premixed and non-premixed flamelet model is developed using the combustion mode index. Finally, the effects of reaction progress variable definition on the flamelet predictions are quantified. A state-of-the-art direct numerical simulation database is employed to challenge the newly developed flamelet models. The tabulated thermo-chemical quantities are compared with the reference direct numerical simulation results througha priorianalyses. Comparisons show that the newly developed flamelet models which take into account strong heat loss effects can predict the gas temperature and species mass fractions correctly. The adiabatic flamelet models over-predict the corresponding thermo-chemical quantities in regions where the interphase heat transfer is significant. Coupled with a linear extrapolation method, the prediction of the gas temperature with the adiabatic flamelet models can be improved. The performance of the multi-mode flamelet model depends on whether the local combustion mode can be correctly identified. The conventional combustion mode index based on the gradients of fuel and oxidizer species mass fractions cannot correctly identify the combustion mode in the entire combustion field.