Conditional statistics of inert droplet effects on turbulent combustion in reacting mixing layers
Conditional statistics of inert droplet effects on turbulent combustion in reacting mixing layers
复制标题
惰性液滴对反应混合层湍流燃烧影响的条件统计
DOI：
10.1080/13647830903288381
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发表时间：
2009
影响因子：
1.3
通讯作者：
Xia J
中科院分区：
文献类型：
--
作者：
Xia J
采用湍流反应混合层的直接数值模拟方法，在多相湍流燃烧的条件矩闭合(CMC)条件下，研究了液滴对多相湍流燃烧的影响。基于涡度厚度，时间发展混合层的初始雷诺数为1000，跟踪到了1600多万个拉格朗日液滴。含有惰性蒸汽质量分数的等量混合物分数清楚地表明了蒸汽稀释对混合物的影响。瞬时场和条件统计量，如单条件标量耗散率、燃气温度<Tg|η>、燃气温度的条件方差<Tg“2|η>和燃料质量分数与燃气温度的条件协方差<YF”Tg“|η>显示了相当大的液滴效应。比较无液滴和有液滴的反应混合层情况，发现后者有明显的消光现象。由此产生的围绕条件均值的大的条件波动与一阶单条件CMC背后的基本假设相矛盾。更复杂的CMC方法，如双重条件或二阶CMC，原则上能够更好地纳入蒸发液滴的影响，但存在重大的建模挑战。在混合分数和归一化气体温度<χ|η，ζ>双重条件下的标量耗散率说明了多相燃烧CMC模型的复杂性。
Direct numerical simulation (DNS) of turbulent reacting mixing layers laden with evaporating inert droplets is used to assess the droplet effects in the context of the conditional moment closure (CMC) for multiphase turbulent combustion. The temporally developing mixing layer has an initial Reynolds number of 1000 based on the vorticity thickness with more than 16 million Lagrangian droplets traced. An equivalent mixture fraction incorporating the inert vapour mass fractions clearly demonstrates the effects of vapour dilution on the mixture. Instantaneous fields and conditional statistics, such as the singly conditioned scalar dissipation rate, the gas temperature 〈Tg|η 〉, conditional variance of the gas temperature 〈Tg”2|η 〉 and conditional covariance between the fuel mass fraction and gas temperature 〈Yf”Tg”|η 〉 show considerable droplet effects. Comparison between the droplet-free and droplet-laden reacting mixing layer cases suggests significant extinction in the latter case. The resulting large conditional fluctuations around the conditional means contradict the basic assumption behind the first-order singly conditioned CMC. More sophisticated CMC approaches, such as doubly conditioned or second-order CMCs are, in principle, better able to incorporate the effects of evaporating droplets, but significant modelling challenges exist. The scalar dissipation rate doubly conditioned on the mixture fraction and a normalized gas temperature 〈 χ | η, ζ 〉 exemplifies the modelling complexity in the CMC of multiphase combustion.
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DOI：
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发表时间：
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期刊：
影响因子：
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作者：
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DOI：
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发表时间：
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