An Experimental Study of Freely Propagating Premixed Flames at Various Lewis Numbers
An Experimental Study of Freely Propagating Premixed Flames at Various Lewis Numbers
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不同路易斯数下自由传播预混火焰的实验研究
DOI：
10.1080/00102200108952148
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发表时间：
2001
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. Boukhalfa
在衰减各向同性湍流中，对不同的Lewis数进行了实验，得到了几种自由传播的预混湍流火焰。利用高速激光薄板层析成像技术，研究了固定u‘/SL0的路易斯数(Le)对火焰锋面结构的影响。这项实验研究也是为了突出在不同的湍流条件和燃料/空气混合物下，湍流预混火焰的火焰锋面几何形状随时间的变化情况。根据层析成像记录，计算了火焰发展每个阶段的火焰表面性质和平均半径，并确定了火焰传播每个阶段的平均整体拉伸和平均燃烧速度。正如渐近理论所预期的那样，在低湍流条件下，优先扩散/拉伸相互作用的影响可以用线性相关来模拟。对于Le∼L，平均燃烧速度随平均火焰伸长略有减小，且Markstein长度与湍流条件无关。对于Le∼L.6和Le∼0.3，层流火焰和湍流火焰的平均燃烧速度随平均拉伸的变化趋势相反。除了高度湍动的氢气/空气火焰u‘/SL0=1.89外，层流火焰中弱拉伸的线性相关性和预测似乎对湍流预混火焰是有效的。对于小的Lewis数值和/或高的u‘/SL0值，结合渐近理论的弱拉伸方法不足以模拟预混湍流燃烧。
Several freely-propagating premixed turbulent flames are experimentally obtained in a decaying isotropic turbulent flow for various Lewis numbers. The high speed laser sheet tomography technique is applied to visualize the temporal evolution of the spatial properties of the flame fronts and to study the influence of the Lewis number (Le) on the flame front structures at fixed u′/SL 0. This experimental study is also performed to highlight the transient effect over time of the flame front geometry of turbulent premixed flames under varying turbulence conditions and fuel/air mixtures. From the tomographic recordings, the flame surface properties and mean radii are calculated at each stage of flame development and allow the mean global stretch and the mean burning velocity at each step of the flame propagation to be determined. As expected from asymptotic theory, the effects of preferential-diffusion/stretch interactions for low turbulent conditions can be modeled according to a linear correlation. For Le∼l, the mean burning velocity decreases slightly with the mean flame stretch, and the Markstein lengths are independent of the turbulent conditions. For Le∼l.6 and Le∼0.3, the mean burning velocity evolution with mean stretch shows an opposite trend both for laminar and turbulent flames. The linear dependence between and predicted for weak stretch in laminar flames appears to be valid for turbulent premixed flames, except for highly turbulent hydrogen/air flames u′/SL 0 = 1.89. For small values of Lewis numbers and/or high values of u′/SL 0, the weakly stretched approach associated with the asymptotic theory is insufficient for modeling premixed turbulent combustion.