Statistical Analysis of Turbulent Flame-Droplet Interaction: A Direct Numerical Simulation Study
Statistical Analysis of Turbulent Flame-Droplet Interaction: A Direct Numerical Simulation Study
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DOI：
10.1007/s10494-015-9652-y
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
D. Wacks;N. Chakraborty;E. Mastorakos
中科院分区：
文献类型：
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作者：
D. Wacks;N. Chakraborty;E. Mastorakos
采用三维直接数值模拟（DNS）方法，对衰减湍流条件下单分散液滴-细水雾的湍流燃烧进行了数值模拟。燃料以液相供应，液滴的蒸发产生气态燃料，用于火焰传播到液滴-薄雾中。研究发现，初始液滴直径、湍流强度和液滴当量比对体积积分燃烧速率、火焰表面积和单位面积燃烧速率有显著影响。发现液滴主要在预热区蒸发，但一些液滴穿透火焰前缘，到达燃烧气体侧，在那里它们蒸发，并且一些所得的燃料蒸气扩散回到火焰前缘。气相中的燃烧过程主要发生在贫燃料模式中，即使对于Pdd> 1。发现贫燃料混合物的概率随着初始液滴直径的增加而增加，因为较大液滴的蒸发较慢，并且这种主要的贫燃料燃烧模式表现出低达姆科勒数燃烧的属性，并且随着液滴直径的增加而引起火焰的增厚。化学反应被发现发生在预混和非预混燃烧模式和非预混燃烧的相对贡献的整体热释放增加液滴尺寸。对火焰传播和燃烧模式的统计特性进行了详细的分析，并对所观察到的特性提供了详细的物理解释。
Turbulent combustion of mono-disperse droplet-mist has been analysed based on three-dimensional Direct Numerical Simulations (DNS) in canonical configuration under decaying turbulence for a range of different values of droplet equivalence ratio (ϕd), droplet diameter (ad) and root-mean-square value of turbulent velocity (u′). The fuel is supplied in liquid phase and the evaporation of droplets gives rise to gaseous fuel for the flame propagation into the droplet-mist. It has been found that initial droplet diameter, turbulence intensity and droplet equivalence ratio can have significant influences on the volume-integrated burning rate, flame surface area and burning rate per unit area. The droplets are found to evaporate predominantly in the preheat zone, but some droplets penetrate the flame front, reaching the burned gas side where they evaporate and some of the resulting fuel vapour diffuses back towards the flame front. The combustion process in gaseous phase takes place predominantly in fuel-lean mode even for ϕd> 1. The probability of finding fuel-lean mixture increases with increasing initial droplet diameter because of slower evaporation of larger droplets and this predominantly fuel-lean mode of combustion exhibits the attributes of low Damköhler number combustion and gives rise to thickening of flame with increasing droplet diameter. The chemical reaction is found to take place under both premixed and non-premixed modes of combustion and the relative contribution of non-premixed combustion to overall heat release increases with increasing droplet size. The statistical behaviours of the flame propagation and mode of combustion have been analysed in detail and detailed physical explanations have been provided for the observed behaviour.