Flame Self-interaction and Flow Topology in Turbulent Homogeneous Mixture n-Heptane MILD Combustion
Flame Self-interaction and Flow Topology in Turbulent Homogeneous Mixture n-Heptane MILD Combustion
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正庚烷湍流均质混合物轻度燃烧中的火焰自相互作用和流动拓扑
DOI：
10.1007/s10494-023-00401-w
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Abo-Amsha K
中科院分区：
文献类型：
--
作者：
Abo-Amsha K
中等或强烈的低氧稀释(温和)燃烧有可能实现高能效和超低排放。该分析采用临界点理论来描述湍流、均匀混合气、正庚烷温和燃烧中的火焰自作用(FSI)事件和流动拓扑结构，并采用简化的化学机理的直接数值模拟(DNS)。用平均曲率和高斯曲率对局部火焰几何形状进行了分类。研究发现，在反应进度变量的所有值下，隧道形成(TF)和隧道关闭(TC)拓扑是最有可能的FSI事件，而未燃烧的火焰(UP)和燃烧的火焰(BP)拓扑主要分别存在于未燃烧和燃烧的混合气中。此外，增加湍流强度并不会导致FSI事件的分布发生显著变化。对流动拓扑分布的研究表明，在所考虑的轻度情况下，不存在与非零扩张率相关的特征。这是由于在温和燃烧情况下，由于温升很小，热膨胀效应可以忽略不计。增加稀释系数会导致所有级别的FSI事件的频率降低。均匀混合气温和燃烧中火焰自作用事件的分布与已报道的常规湍流预混燃烧的分布有很大不同。
Moderate or Intense Low-oxygen Dilution (MILD) combustion has potential to achieve both high energy efficiency and ultra-low emissions. This analysis adopts the critical point theory to characterise the Flame-Self Interaction (FSI) events and flow topologies in turbulent, homogeneous mixture, n-Heptane MILD combustion using Direct Numerical Simulations (DNS) with reduced chemical mechanism. The local flame geometry has also been categorised using the mean and Gauss curvatures. It was found that the Tunnel Formation (TF) and Tunnel Closure (TC) topologies are the most probable FSI events at all values of the reaction progress variablec, while the Unburned Pocket (UP) and Burned Pocket (BP) topologies were mostly present towards the unburned and burned mixtures of the flame, respectively. Moreover, increasing the turbulence intensity did not result in any significant changes in the distribution of FSI events. Investigation of the flow topology distribution showed that the features associated with non-zero dilatation rate did not exist in the MILD cases considered. This is a consequence of the negligible thermal expansion effect due to the small temperature rise in MILD combustion cases. Increasing the dilution factor caused a reduction in the frequency of FSI events for allclevels. The distributions of flame self-interaction events in homogeneous mixture MILD combustion have been found to be significantly different from previously reported distributions for conventional turbulent premixed combustion.
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