Flame resolved simulation of a turbulent premixed bluff-body burner experiment. Part I: Analysis of the reaction zone dynamics with tabulated chemistry
Flame resolved simulation of a turbulent premixed bluff-body burner experiment. Part I: Analysis of the reaction zone dynamics with tabulated chemistry
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DOI：
10.1016/j.combustflame.2017.02.011
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发表时间：
2017-06
影响因子：
4.4
通讯作者：
F. Proch;P. Domingo;L. Vervisch;A. Kempf
中科院分区：
文献类型：
--
作者：
F. Proch;P. Domingo;L. Vervisch;A. Kempf
本文介绍了在剑桥大学和桑迪亚国家实验室进行的湍流贫燃甲烷-空气预混钝体燃烧器的高分辨率模拟结果。笛卡尔计算网格由16亿个单元组成，分辨率为100 μ m，足以捕获500 μ m的层流（热）火焰厚度。燃烧过程采用预混火焰生成歧管（PFGM）模型。通过调查火焰和速度尺度的分辨率来评估模拟的质量，结果表明，在火焰中直接数值模拟（DNS）的意义上解决了相关尺度。通过比较速度，温度和主要物种的质量分数与实验结果的时间统计模拟验证。结果表明，燃烧状态随距燃烧器的距离和反应进程而变化。系综平均统计，有条件的手段和平均值沿着湍流火焰与参考数据从无应变预混一维火焰进行了比较。进行了分析，相对于以前的调查结果，从DNS的更简单的火焰配置具有合成湍流。得出的结论是，主要的物理性能是可比的。换句话说，以前DNS研究中的大多数典型案例的发现都是相关的，至少对于这里研究的实验室规模的射流火焰来说是如此。火焰法向应变被发现是对齐的最压缩应变率。的平均主曲率的进步变量等值面主要是零，并偏向正值，湍流火焰结构主要是稍微变薄相比，层流的。火焰的位移速度被发现采取部分负值。位移速度和消耗速度之间缺乏相关性也被报道，相关性仅考虑扩散通量的法向分量来实现。
Results from a highly resolved simulation are presented for a turbulent lean premixed methane-air bluff-body burner investigated experimentally at Cambridge University and Sandia National Laboratories. The Cartesian computational grid consists of 1.6 billion cells with a resolution of 100 μ m, which is sufficient to capture the laminar (thermal) flame thickness of 500 μ m. The combustion process is modeled with premixed flamelet generated manifolds (PFGM). The quality of the simulation is assessed by investigating the resolution of the flame-and velocity scales, it is demonstrated that the relevant scales are resolved in a direct numerical simulation (DNS) sense in the flame. The simulation is validated by comparing temporal statistics of velocity, temperature and major species mass fractions against experimental results. It is shown that the combustion regime varies with the distance from the burner and the progress of the reaction. Ensemble-averaged statistics, conditional means and averages along turbulent flamelets are compared against reference data from unstrained premixed one-dimensional flames. The analysis is carried out with respect to previous findings from DNS of much simpler flame configurations featuring synthetic turbulence. It is concluded that the major physical properties are comparable. In other words, most of the findings from previous DNS studies for canonical cases are relevant, at least for the lab-scale jet-flame examined here. The flame normal strain is found to be aligned with the most compressive strain rate. The mean principal curvature of the progress variable iso-surfaces is predominantly zero and skewed towards positive values, the turbulent flame structure is mainly slightly thinned compared to the laminar one. The displacement speed of the flame is found to take partially negative values. The lack of correlation between the displacement speed and the consumption speed is also reported, the correlation being achieved considering the normal component of the diffusive flux only.