Turbulence effects during evaporation of drops in clusters
Turbulence effects during evaporation of drops in clusters
复制标题
簇状液滴蒸发过程中的湍流效应
DOI：
10.1016/0017-9310(88)90278-5
复制
发表时间：
1988
影响因子：
5.2
通讯作者：
K. Harstad
中科院分区：
文献类型：
--
作者：
J. Bellan;K. Harstad
本文提出了团簇中液滴蒸发的模型，以及团簇与周围气相的交换过程。该模型是作为一个亚尺度模型在喷雾蒸发和燃烧的计算，从而只描述了全球的集群行为的特点。团簇中的气体压力在蒸发过程中保持恒定，因此团簇的体积和团簇内的液滴数密度发生变化。考虑了两种湍流模型。第一个描述了在最初没有湍流的环境中的团簇蒸发，并且允许湍流随着时间的推移而建立。第二个模型描述了团簇蒸发的环境中，湍流最初存在。与这些模型得到的结果表明，湍流增强蒸发，是一个控制因素，在蒸发的非常密集的集群;例子显示，其中与第一湍流模型的饱和度得到完全蒸发之前，而相反的是获得与第二湍流模型。随着初始空气/燃料质量比的增加，湍流历史和液滴与气体之间的初始相对速度可以控制蒸发。结果表明，蒸发时间随初始湍流度或相对速度的增加而减小。当初始空气/燃料质量比进一步增加并且初始液滴数密度福尔斯落在稀区时，上述参数都不能控制蒸发。此外，蒸发时间随液滴的密集簇的簇的尺寸减小而减小，而对于液滴的稀簇，尺寸不是控制因素。这些结果的实际意义进行了讨论。
A model of droplet evaporation in clusters and the exchange processes between the cluster and the gas phase surrounding it are presented. This model is developed for use as a subscale model in calculations of spray evaporation and combustion and thus described only global features of cluster behavior. The gas pressure in the cluster remains constant during evaporation and as a result the volume of the cluster and the drop number density inside the cluster vary. Two turbulence models are considered. The first one describes cluster evaporation in surroundings initially devoid of turbulence and turbulence is allowed to build up with time. The second model describes cluster evaporation in surroundings where turbulence is present initially. The results obtained with these models show that turbulence enhances evaporation and is a controlling factor in the evaporation of very dense clusters; examples are shown where with the first turbulence model saturation was obtained before complete evaporation whereas the opposite was obtained with the second turbulence model. As the initial air/fuel mass ratio increases, both turbulence history and the initial relative velocity between drops and gases can control evaporation. It is shown that the evaporation time decreases with an initial increase in turbulence levels or relative velocity. When the initial air/fuel mass ratio increases further and the initial drop number density falls within the dilute regime, neither of the above parameters can control evaporation. Moreover, the evaporation time decreases with the decreasing size of the cluster for dense clusters of drops, whereas for dilute clusters of drops the size is not a controlling factor. The practical implications of these results are discussed.