Characterization of the local flame structure and the flame surface density for freely propagating premixed flames at various lewis numbers
Characterization of the local flame structure and the flame surface density for freely propagating premixed flames at various lewis numbers
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不同刘易斯数下自由传播预混火焰的局部火焰结构和火焰表面密度的表征
DOI：
10.1080/713713011
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发表时间：
2002
影响因子：
1.9
通讯作者：
A. Boukhalfa
中科院分区：
文献类型：
--
作者：
B. Renou;A. Mura;E. Samson;A. Boukhalfa
采用激光片层层析成像技术和图像处理技术对自由传播预混湍流火焰的局部火焰结构和火焰面密度进行了测量。不同的燃料/空气混合物（甲烷，丙烷和氢气）已连续火花点火在大气压下，以评估热扩散效应的影响，其特征在于刘易斯数，在准恒定的比例u′S L 0。从瞬时火焰前锋的位置和一维的平均进展变量分布，空间统计，包括湍流火焰刷，平均取向因子，和火焰前锋的法向矢量的分量的特征在于，并与文献中的数值和实验结果进行了比较。火焰面密度的时间演变也确定了几种方法和分析方面的最大火焰面密度的演变和最大火焰面密度的位置。它清楚地表明，最大火焰面密度随着火焰的传播而减小，并保持独立的刘易斯数在C2C空间。文中还给出了湍流度u′ SL 0对最大火焰面密度的影响，并与文献中的各种结果进行了比较。峰值位置略小于对称值<$C <$=0.5，并随着火焰传播而略有增加。还提出了表征湍流扩散性质（梯度或反梯度）的Bray数N B的估计，以表征Bray C的湍流通量。
The local flame structure and the flame surface density for freely propagating premixed turbulent flames are measured by laser sheet tomography and image processing techniques. Different fuel/air mixtures (methane, propane, and hydrogen) have been successively spark-ignited at atmospheric pressure in order to evaluate the influence of thermodiffusive effects characterized by the Lewis number, at quasi-constant ratio u′S L 0 . From the instantaneous flame front positions and the mono-dimensional mean progress variable distribution, spatial statistics including the turbulent flame brush, the mean orientation factors, and the components of the normal vector to the flame front have been characterized and compared with numerical and experimental results available in the literature. The temporal evolution of the flame surface density was also determined by several approaches and analyzed in terms of maximum flame surface density evolution and location of maximum flame surface density. It clearly appears that the maximum flame surface density decreases as the flame propagates and remains independent of the Lewis number in the ⟨C⟩ space. The influence of the turbulence level u′S L 0 on the maximum flame surface density is also presented and compared with various results available in the literature. The peak location is a little less than the symmetrical value ⟨C⟩=0.5, and increases slightly as the flame propagates. An estimation of the Bray number, N B , which characterizes the nature of the diffusion by turbulence (gradient or counter-gradient), is also proposed in order to characterize the turbulent flux of ⟨C⟩ (or Σ).