MODELING LIFTED JET FLAMES IN A HEATED COFLOW USING AN OPTIMIZED EDDY DISSIPATION CONCEPT MODEL
MODELING LIFTED JET FLAMES IN A HEATED COFLOW USING AN OPTIMIZED EDDY DISSIPATION CONCEPT MODEL
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DOI：
10.1080/00102202.2014.1002836
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发表时间：
2015-01-01
影响因子：
1.9
通讯作者：
Tian, Z. F.
中科院分区：
文献类型：
--
作者：
Evans, M. J.;Medwell, P. R.;Tian, Z. F.
适度或强烈的低氧稀释（MILD）燃烧已经被确立为具有改进的热效率和减少的污染物排放（包括NOx和烟灰）的燃烧状态。温和的燃烧一直是许多实验研究的主题，并提出了一个挑战，计算建模由于强烈的连续性化学耦合内的均匀反应区。热同向流（JHC）燃烧器中的射流火焰模型通常使用涡流耗散概念（EDC）燃烧模型取得了有限的成功，该模型以较低的计算费用结合了有限速率动力学。提出了一个改进的EDC模型，成功地模拟了9%O-2同向流中的乙烯-氮气火焰。通过系统研究发现，将参数C-tau和C-xi从默认值0.4082和2.1377调整到3.0和1.0，在这些条件下EDC模型的性能得到显著改善。这种改进的EDC模型随后被应用到其他乙烯和甲烷为基础的燃料射流在一系列的同向流氧化剂流的条件。修改后的EDC提供的结果相比，更复杂，计算昂贵，运输概率密度函数（PDF）的方法。优化的EDC模型给出更好的协议与实验测量的温度，羟基（OH），和甲醛（CH 2 O）的配置文件。随后使用OH* 和CH* 的动力学机制定义所选火焰的视觉边界，与实验观察结果吻合良好。该模型也出现更强大的变化，在燃料喷射入口温度和湍流强度比标准的EDC模型在以前的研究中进行了试验。新修改的模型的加热同向流边界的化学成分的敏感性也表现出鲁棒性和定性协议与以前的作品。所提出的修改后的EDC模型提供了改进的协议与实验数据的配置文件比以前已经实现，并提供了一个可行的替代方案，显着更昂贵的计算建模方法，在一个加热和vitated coflow的火焰。最后，在这种配置中实验观察到的视觉提升火焰行为被复制，这是过去使用EDC模型没有成功再现的现象。
Moderate or intense low oxygen dilution (MILD) combustion has been established as a combustion regime with improved thermal efficiency and decreased pollutant emissions, including NOx and soot. MILD combustion has been the subject of numerous experimental studies, and presents a challenge for computational modeling due to the strong turbulence-chemistry coupling within the homogeneous reaction zone. Models of flames in the jet in hot coflow (JHC) burner have typically had limited success using the eddy dissipation concept (EDC) combustion model, which incorporates finite-rate kinetics at low computational expense. A modified EDC model is presented, which successfully simulates an ethylene-nitrogen flame in a 9% O-2 coflow. It is found by means of a systematic study in which adjusting the parameters C-tau and C-xi from the default 0.4082 and 2.1377 to 3.0 and 1.0 gives significantly improved performance of the EDC model under these conditions. This modified EDC model has subsequently been applied to other ethylene-and methane-based fuel jets in a range of coflow oxidant stream conditions. The modified EDC offers results comparable to the more sophisticated, and computationally expensive, transport probability density function (PDF) approach. The optimized EDC models give better agreement with experimental measurements of temperature, hydroxyl (OH), and formaldehyde (CH2O) profiles. The visual boundary of a chosen flame is subsequently defined using a kinetic mechanism for OH* and CH*, showing good agreement with experimental observations. This model also appears more robust to variations in the fuel jet inlet temperature and turbulence intensity than the standard EDC model trialed in previous studies. The sensitivity of the newly modified model to the chemical composition of the heated coflow boundary also demonstrates robustness and qualitative agreement with previous works. The presented modified EDC model offers improved agreement with experimental data profiles than has been achieved previously, and offers a viable alternative to significantly more computationally expensive modeling methods for lifted flames in a heated and vitiated coflow. Finally, the visually lifted flame behavior observed experimentally in this configuration is replicated, a phenomenon that has not been successfully reproduced using the EDC model in the past.