Large eddy simulation/dynamic thickened flame modeling of a high Karlovitz number turbulent premixed jet flame
Large eddy simulation/dynamic thickened flame modeling of a high Karlovitz number turbulent premixed jet flame
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DOI：
10.1016/j.proci.2018.06.228
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发表时间：
2019
影响因子：
3.4
通讯作者：
Wang Han;Haiou Wang;G. Kuenne;E. Hawkes;Jacqueline H. Chen;J. Janicka;C. Hasse
中科院分区：
文献类型：
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作者：
Wang Han;Haiou Wang;G. Kuenne;E. Hawkes;Jacqueline H. Chen;J. Janicka;C. Hasse
由于强烈的湍流和相对较弱的火焰之间的复杂的多尺度相互作用，湍流预混火焰在薄和破碎的反应区制度表现出强烈的有限速率化学和应变效应，因此具有挑战性的模型。在这项工作中，一个实验室预混射流火焰在破碎的反应区，最近已经研究了使用直接数值模拟（DNS），建模使用大涡模拟（LES）/动态增厚火焰（DTF）的方法与详细的化学。由于强烈的燃烧-化学相互作用，其特征在于高的Karlovitz数（Ka），大量的火焰增厚的存在，需要DTF模型，以自适应的方式，基于火焰尺度的局部分辨率的火焰。这里，使用合适的火焰传感器和应变敏感火焰厚度来分别自动确定增厚位置和增厚因子。为了解释有限速率化学和应变效应，化学以两种不同的方式描述：（1）详细的化学表示为完全传输和化学（FTC），和（2）基于应变预混小火焰（SPF）模型的列表化学。通过与DNS对同一火焰的详细后验比较，评估了增强LES/DTF方法模拟高Kapremixed火焰的性能。结果表明，LES/DTF/FTC模型能够再现高湍流预混火焰的大部分特征，包括CO和NO的准确预测。LES/DTF/SPF模型具有捕获强湍流对火焰结构的影响的潜力，并且以合理的计算成本提供了对污染物排放的合理预测。为了确定气动应变的影响，湍流火焰结构进行了分析，并与无应变和应变预混小火焰的解决方案进行了比较。结果表明，在用表格法模拟高Kapremixed火焰时，应考虑详细的应变效应。
Due to the complex multiscale interaction between intense turbulence and relatively weak flames, turbulent premixed flames in the thin and broken reaction zones regimes exhibit strong finite-rate chemistry and strain effects and are hence challenging to model. In this work, a laboratory premixed jet flame in the broken reaction zone, which has recently been studied using direct numerical simulation (DNS), is modeled using a large eddy simulation (LES)/dynamic thickened flame (DTF) approach with detailed chemistry. The presence of substantial flame thickening due to strong turbulence-chemistry interactions, which can be characterized by a high Karlovitz number (Ka), requires the DTF model to thicken the flame in an adaptive way based on the local resolution of flame scales. Here, an appropriate flame sensor and strain-sensitive flame thickness are used to automatically determine the thickening location and thickening factor, respectively. To account for finite-rate chemistry and strain effects, the chemistry is described in two different ways: (1) detailed chemistry denoted as full transport and chemistry (FTC), and (2) tabulated chemistry based on a strained premixed flamelet (SPF) model. The performance of the augmented LES/DTF approach for modeling the highKapremixed flame is assessed through detaileda posterioricomparisons with DNS of the same flame. It is found that the LES/DTF/FTC model is capable of reproducing most features of the highKaturbulent premixed flame including accurate CO and NO prediction. The LES/DTF/SPF model has the potential to capture the impact of strong turbulence on the flame structure and provides reasonable prediction of pollutant emissions at a reasonable computational cost. In order to identify the impact of aerodynamic strain, the turbulent flame structure is analyzed and compared with unstrained and strained premixed flamelet solutions. The results indicate that detailed strain effects should be considered when using tabulated methods to model highKapremixed flames.