Lewis Number Effects on Flame Speed Statistics in Spherical Turbulent Premixed Flames
Lewis Number Effects on Flame Speed Statistics in Spherical Turbulent Premixed Flames
复制标题
球形湍流预混火焰中火焰速度统计的刘易斯数效应
DOI：
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发表时间：
2020
影响因子：
2.4
通讯作者：
N. Chakraborty
中科院分区：
文献类型：
--
作者：
G. Ozel;M. Klein;N. Chakraborty
利用三维直接数值模拟数据，分析了在统计相似的流动条件下，特征Lewis数对球形膨胀湍流预混火焰密度加权置换速度和消耗速度的影响。研究发现，火焰起皱和燃烧的程度随着HBox{Le}和Le的减小而增加，这反映在密度加权位移的平均值和最大可能值以及消耗速度的增加趋势上。此外，在所有情况下，密度加权置换速度的边际概率密度函数显示获得负值的有限概率，而消耗速度保持确定性正。标量梯度和温度的应变率和曲率依赖于HBox{Le}，这些统计量以及应变率和曲率之间的相互关系影响了消耗速度的局部应变率和曲率响应，以及密度加权位移速度的反应和法向扩散分量。密度加权位移速度与曲率呈负相关，而密度加权位移速度与切向应变率呈正相关。在HBox{Le}=0.8$$Le=0.8的情况下，热和质量的微分扩散引起的温度与曲率之间的正相关导致了消耗速度与曲率之间的正相关，而在$HBox{Le}=1.2$$Le=1.2的火焰中，这些关系是负的。密度加权置换速度的统计行为已经被用来证明Damköhler的第一个假设对于球状扩张的湍流预混火焰并不严格成立。
The influences of characteristic Lewis number $$ hbox{Le} $$ Le on the statistics of density-weighted displacement speed and consumption speed in spherically expanding turbulent premixed flames have been analysed using three-dimensional direct numerical simulations data for $$ hbox{Le} = 0.8 $$ Le = 0.8 , 1.0 and 1.2 under statistically similar flow conditions. It has been found that the extents of flame wrinkling and burning increase with decreasing $$ hbox{Le} $$ Le , which is reflected in increasing trends of mean and most probable values of both density-weighted displacement and consumption speed. Moreover, in all cases the marginal probability density functions of density-weighted displacement speed show finite probabilities of obtaining negative values, whereas consumption speed remains deterministically positive. The strain rate and curvature dependences of scalar gradient and temperature have been found to be strongly dependent on $$ hbox{Le} $$ Le , and these statistics, along with the interrelation between strain rate and curvature, influence the local strain rate and curvature responses of consumption speed and both reaction and normal diffusion components of density-weighted displacement speed. Density-weighted displacement speed and curvature have been found to be negatively correlated, whereas positive correlations are obtained between density-weighted displacement speed and tangential strain rate for all flames considered here. The positive correlation between temperature and curvature arising from differential diffusion of heat and mass in the $$ hbox{Le} = 0.8 $$ Le = 0.8 case induces a positive correlation between consumption speed and curvature, whereas these correlations are negative in the $$ hbox{Le} = 1.2 $$ Le = 1.2 flame. The statistical behaviour of density-weighted displacement speed has been utilised to demonstrate that Damköhler’s first hypothesis does not strictly hold for spherically expanding turbulent premixed flames.
使用火焰表面密度传输深入了解预混湍流燃烧中的弯曲效应
影响因子：
1.9
作者：
Ahmed U
通讯作者：
Ahmed U
影响因子：
4.4
作者：
N. Chakraborty;G. Hartung;M. Katragadda;C. Kaminski
通讯作者：
N. Chakraborty;G. Hartung;M. Katragadda;C. Kaminski