Large Eddy Simulation of soot evolution in turbulent reacting flows: Strain-Sensitive Transport Approach for Polycyclic Aromatic Hydrocarbons
Large Eddy Simulation of soot evolution in turbulent reacting flows: Strain-Sensitive Transport Approach for Polycyclic Aromatic Hydrocarbons
复制标题
湍流反应流中烟灰演化的大涡模拟：多环芳烃的应变敏感传输方法
DOI：
10.1016/j.combustflame.2020.07.008
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发表时间：
2020
影响因子：
4.4
通讯作者：
M. Mueller
中科院分区：
文献类型：
--
作者：
Suo Yang;Jeffry K. Lew;M. Mueller
多环芳烃(PAH)由于其缓慢的生成化学作用，被限制在空间间断的低标量耗散率的区域。这些区域的长度尺度在Kolmogorov尺度或更小的数量级，其中分子扩散主导湍流混合，而与大尺度湍流雷诺数无关。提出了一种应变敏感性参数来识别这类物种。然后发展了应变敏感输运方法(SSTA)来模拟非预混火焰面方程中的这种差异输运。具体来说，应变敏感物种用其非单位分子有效Lewis数来模拟，而其余物种则用单位有效Lewis数来模拟。对非预混火炬溶液的优先分析表明，火焰温度和应变不敏感物质(例如，主要燃烧产物、乙炔等)。所提出的SSTA剖面与单位有效Lewis数方法得到的轮廓非常接近，但应变敏感物种(例如，萘)的质量分数与单位有效Lewis数方法相比有显著的修正，并与直接数值模拟(DNS)数据一致。这种新的SSTA模型在大涡模拟(LES)框架下实现，应用于一系列实验室尺度的湍流非预混喷流火焰，并通过与温度和碳烟体积分数的实验测量进行比较来验证。统一有效Lewis数方法和SSTA模型预测的温度与实验数据吻合较好，但非单位分子有效Lewis数方法高估了火焰长度。与统一有效Lewis数方法相比，从碳烟体积分数的上游增长和峰值沿中心线的位置来看，SSTA预测的碳烟体积分数的空间分布与实验测量结果更吻合，这两者都强烈依赖于对多环芳烃质量分数的准确预测。最大碳烟体积分数受影响最小，与实验测量结果吻合较好。最后，利用这一新的SSTA模型，分析了整体应变率对湍流非预混黑喷流火焰的影响，发现即使PAH与整体应变率成反比，碳烟体积分数也不一定与整体应变率成反比，这是因为乙炔表面生长速率系数随着整体应变率的增加而增加。
Polycyclic Aromatic Hydrocarbons (PAH) are confined to spatially intermittent regions of low scalar dissipation rates due to their slow formation chemistry. The length scales of these regions are on the order of the Kolmogorov scale or smaller, where molecular diffusion dominates over turbulent mixing irrespective of the large-scale turbulent Reynolds number. A strain-sensitivity parameter is proposed to identify such species. A Strain-Sensitive Transport Approach (SSTA) is then developed to model this differential transport in the nonpremixed flamelet equations. Specifically, the strain-sensitive species are modeled with their non-unity molecular effective Lewis numbers, while the remaining species are modeled with unity effective Lewis numbers. Ana priorianalysis of nonpremixed flamelet solutions reveals that the flame temperature and strain-insensitive species (e.g., major products of combustion, acetylene, etc.) profiles from the proposed SSTA closely match those from the unity effective Lewis number approach, but the mass fractions of strain-sensitive species (e.g., naphthalene) are significantly modified compared to the unity effective Lewis number approach and are consistent with Direct Numerical Simulation (DNS) data. This new SSTA model is implemented within a Large Eddy Simulation (LES) framework, applied to a series of laboratory-scale turbulent nonpremixed sooting jet flames, and validated via comparisons with experimental measurements of temperature and soot volume fraction. Both the unity effective Lewis number approach and SSTA model provide temperature predictions in good agreement with the experimental data, but the non-unity molecular effective Lewis number approach overpredicts the flame length. Compared to the unity effective Lewis number approach, the spatial distribution of soot volume fraction predicted by SSTA is in better agreement with the experimental measurements in terms of the upstream growth of the soot volume fraction and the location of its peak value along the centerline, both of which strongly depend on accurate predictions of the PAH mass fraction. The maximum soot volume fraction is minimally influenced and in good agreement with the experimental measurements. Finally, with this new SSTA model, the influence of global strain rate on turbulent nonpremixed sooting jet flames is analyzed to find that, even though PAH is inversely proportional to the global strain rate, the soot volume fraction may not be inversely proportional to the global strain rate due to an increase in the acetylene surface growth rate coefficient with global strain rate.
影响因子：
4.4
作者：
Achim Wick;A. Attili;F. Bisetti;H. Pitsch
通讯作者：
Achim Wick;A. Attili;F. Bisetti;H. Pitsch