Assessment of Bray Moss Libby formulation for premixed flame-wall interaction within turbulent boundary layers: Influence of flow configuration
Assessment of Bray Moss Libby formulation for premixed flame-wall interaction within turbulent boundary layers: Influence of flow configuration
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DOI：
10.1016/j.combustflame.2021.111575
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发表时间：
2021-07-17
影响因子：
4.4
通讯作者：
Klein, Markus
中科院分区：
文献类型：
--
作者：
Ahmed, Umair;Chakraborty, Nilanjan;Klein, Markus
对两种不同流动构型的预混火焰在充分发展的湍流边界层中与化学惰性等温壁面相互作用进行了三维直接数值模拟（DNS）。第一种配置是倾斜火焰壁相互作用（FWI）的V型火焰在湍流通道流和第二种配置是迎面淬火平面火焰在湍流边界层。这些模拟代表了大气条件下单位刘易斯数下化学计量的甲烷-空气混合物。这些模拟的非反应条件下的湍流代表基于摩擦速度的雷诺数Re-tau = 110。在FWI过程中的进展变量，温度和密度的平均值的统计行为的差异已报告的两种配置。据发现，平均火焰刷增厚在近壁区域导致显着偏离严格的布雷莫斯利比（BML）制定限制在FWI过程中，这是反映在概率密度函数（PDF）分布的C两个火焰配置。还研究了BML公式中雷诺平均过程变量（c）在横杠上的封闭性和过程变量（c“（2））在波浪线上的Favre平均方差，发现即使当火焰远离壁面代表高Damkohler数预混湍流燃烧时，也需要对这些封闭性进行修改以考虑FWI过程。此外，根据DNS数据对两种火焰构型的基于火焰表面密度（FSD）的平均反应速率闭合所需的量的统计行为进行了询问，包括火焰取向因子σ（y）、小火焰长度尺度L-y和火焰拉伸因子I-0。的火焰长度尺度和拉伸因子提取的DNS数据进行比较，这些数量在文献中提出的封闭。结果发现，sigma（y）在两种情况下都表现出显著的空间变化。已经确定了L-y和I-0的现有封闭物，其表现出与DNS数据的最佳定量一致性。已经发现，L-y和I-0的模型有进一步改进的余地，以便能够在湍流边界层内的FWI过程期间满意地预测这些量。(C)2021燃烧研究所爱思唯尔公司出版All rights reserved.
Three-dimensional direct numerical simulations (DNS) of two different flow configurations have been performed for premixed flames interacting with chemically inert isothermal walls at the unburned gas temperature in fully developed turbulent boundary layers. The first configuration is an oblique flame-wall interaction (FWI) of a V-flame in a turbulent channel flow and the second configuration is a head-on quenching planar flame in a turbulent boundary layer. These simulations are representative of stoichiometric methane-air mixture at unity Lewis number under atmospheric conditions. The turbulence in the non-reacting conditions for these simulations is representative of the friction velocity based Reynolds number of Re-tau = 110. Differences in the statistical behaviours of the mean values of progress variable, temperature, and density during the FWI process have been reported for the two configurations. It is found that the mean flame brush thickens in the near wall region leading to significant departures from the strict Bray Moss Libby (BML) formulation limit during the FWI process and that is reflected in the probability density function (PDF) distributions of c for both flame configurations. The closures from the BML formulation for Reynolds averaged progress variable (c) over bar and the Favre averaged variance of the progress variable (c ''(2)) over tilde have also been investigated and it is found that these closures need to be modified to account for the FWI process even when the flame away from the wall represents high Damkohler number premixed turbulent combustion. Furthermore, the statistical behaviours of the quantities required for Flame Surface Density (FSD) based mean reaction rate closure including the flame orientation factor sigma(y), the flamelet length scale L-y and the flame stretch factor I-0 have been interrogated from the DNS data for the two flame configurations. The flamelet length scale and the stretch factor extracted from the DNS data are compared with the closures for these quantities proposed in the literature. It is found that sigma(y) exhibits significant spatial variation for both cases. The existing closures for L-y and I-0 which exhibit the best quantitative agreement with DNS data have been identified. It has been found that the models for L-y and I-0 have scopes for further improvement to enable satisfactory predictions of these quantities during the FWI process within turbulent boundary layers. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.