Flame self-interactions in globally stoichiometric spherically expanding flames propagating into fuel droplet-mists
Flame self-interactions in globally stoichiometric spherically expanding flames propagating into fuel droplet-mists
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DOI：
10.1016/j.proci.2020.05.025
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发表时间：
2021-04-10
影响因子：
3.4
通讯作者：
Chakraborty, Nilanjan
中科院分区：
文献类型：
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作者：
Ozel-Erol, Gulcan;Ahmed, Umair;Chakraborty, Nilanjan
为了研究与火焰自作用事件相关的火焰拓扑结构的分布，建立了一个统计球形火焰传播到单一尺寸液滴混合物中的三维直接数值模拟数据库，该数据库的总体(即气+液)当量比为1。分析了初始液滴直径和湍流强度的不同取值对火焰自作用统计量的影响。在相同的初始燃烧气体半径和湍流强度下，还考虑了球状膨胀的化学计量预混气体火焰，以便与传播到液滴混合物中的情况进行比较。研究发现，对于湍流预混火焰和湍流强度较小的液滴情况，与火焰自相互作用有关的拓扑结构主要发生在靠近火焰锋面的燃烧气体侧，尽管隧道闭合/形成拓扑在预混火焰中占主导地位，而在液滴情况下则是未燃烧的混合袋状拓扑。实验结果表明，湍流强度和液滴直径都会影响火焰拓扑结构的分布。对于高度湍动的喷雾火焰，火焰自作用事件主要发生在预热区。结果表明，除了低湍流强度下的液滴情况外，在所有情况下，隧道的形成和闭合拓扑结构的出现都决定着未燃烧和燃烧的混合袋的可用性。火焰自作用事件的发生频率随着湍流强度和液滴直径的增大而增加。湍流预混和液滴情况下火焰自相互作用事件的性质和分布的不同可能对基于火焰表面的模拟方法的可能扩展产生重要影响，以模拟液滴混合物中的湍流燃烧。爱思唯尔公司出版，版权所有。
A three-dimensional Direct Numerical Simulation (DNS) database of statistically spherical flames propagating into the mono-sized droplet-laden mixtures for an overall (i.e. gaseous + liquid phases) equivalence ratio of unity has been considered to investigate the distribution of flame topologies associated with flame self-interaction events. The analysis has been carried out for different values of initial droplet diameters and turbulence intensities to demonstrate their influences on the statistics of flame self-interactions. Spherically expanding stoichiometric premixed gaseous flames have also been additionally considered for the same initial burned gas radius and turbulence intensities for the purpose of comparison with the cases propagating into droplet-laden mixtures. It has been found that the topologies associated with flame self-interaction predominantly occur close to burned gas side of the flame front for turbulent premixed flames and also for droplet cases with small turbulence intensities, although tunnel closure/formation topologies are prevalent in premixed flames in contrast to unburned mixture pocket type topologies in the droplet cases. The distribution of the flame topologies has been observed to be influenced by both turbulence intensity and droplet diameter. The flame self-interaction events have mostly been found in the preheat zone for highly turbulent spray flames. It has been found that the occurrence of tunnel formation and closure topologies dominates over the availability of the unburned and burned mixture pockets in all cases except for the droplet cases under low turbulence intensities. The frequency of flame self-interaction events increases with increasing turbulence intensity and droplet diameter. The differences in the nature and distributions of flame self-interaction events between turbulent premixed and droplet cases are likely to have important implications on the possible extension of flame surface based modelling methodologies for simulating turbulent combustion in droplet-laden mixtures.(c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.