Effects of Lewis number on flame surface density transport in turbulent premixed combustion
Effects of Lewis number on flame surface density transport in turbulent premixed combustion
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DOI：
10.1016/j.combustflame.2011.01.011
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发表时间：
2011-09-01
影响因子：
4.4
通讯作者：
Cant, R. S.
中科院分区：
文献类型：
--
作者：
Chakraborty, Nilanjan;Cant, R. S.
利用直接数值模拟（DNS）获得的数据库研究了湍流预混火焰中火焰面密度（FSD）的输运。本文研究了在刘易斯数从0.6到1.2的范围内三维自由传播发展的统计平面湍流预混火焰。简化的化学已被使用，重点是刘易斯数对FSD运输的影响，在雷诺平均封闭模型的背景下。在相同的湍流初始条件下，低刘易斯数的火焰表现出FSD的反梯度输运，而高刘易斯数的火焰则倾向于表现出FSD的梯度输运。较强的放热效应较低的刘易斯数的火焰被发现，导致增加的正（负）值的膨胀率（法向应变率）项在FSD传输方程与减少刘易斯数。发现火焰曲率对FSD输运的贡献受刘易斯数对反应进程变量梯度大小的曲率依赖性以及位移速度的反应和正常扩散分量的影响显著。的FSD运输方程的各个方面的建模进行了详细的分析和现有模型的性能进行评估方面组装从DNS数据中提取的相应数量的条款。基于此评估，确定合适的模型，这些模型能够解决不统一的刘易斯数对FSD运输的影响，并在必要时建议新的或修改的模型。(C)2011燃烧研究所爱思唯尔公司出版All rights reserved.
The transport of flame surface density (FSD) in turbulent premixed flames has been studied using a database obtained from Direct Numerical Simulation (DNS). Three-dimensional freely propagating developing statistically planar turbulent premixed flames have been examined over a range of global Lewis numbers from 0.6 to 1.2. Simplified chemistry has been used and the emphasis is on the effects of Lewis number on FSD transport in the context of Reynolds-averaged closure modelling. Under the same initial conditions of turbulence, flames with low Lewis numbers are found to exhibit counter-gradient transport of FSD, whereas flames with higher Lewis numbers tend to exhibit gradient transport of FSD. Stronger heat release effects for lower Lewis number flames are found to lead to an increase in the positive (negative) value of the dilatation rate (normal strain rate) term in the FSD transport equation with decreasing Lewis number. The contribution of flame curvature to FSD transport is found to be influenced significantly by the effects of Lewis number on the curvature dependence of the magnitude of the reaction progress variable gradient, and on the combined reaction and normal diffusion components of displacement speed. The modelling of the various terms of the FSD transport equation has been analysed in detail and the performance of existing models is assessed with respect to the terms assembled from corresponding quantities extracted from DNS data. Based on this assessment, suitable models are identified which are able to address the effects of non-unity Lewis number on FSD transport, and new or modified models are suggested wherever necessary. (C) 2011 The Combustion Institute. Published by Elsevier Inc. All rights reserved.