Analysis of the development of the flame brush in turbulent premixed spherical flames
Analysis of the development of the flame brush in turbulent premixed spherical flames
复制标题
湍流预混球形火焰中火焰刷的发展分析
DOI：
10.1016/j.combustflame.2021.111640
复制
发表时间：
2021
影响因子：
4.4
通讯作者：
Bisetti, Fabrizio
中科院分区：
文献类型：
--
作者：
Kulkarni, Tejas;Bisetti, Fabrizio
湍流火焰刷的厚度是预混湍流燃烧建模的核心，湍流扩散理论经常被应用于解释刷的生长，并取得了不同的成功。然而，大量的研究表明，刷的发展不同的分散的材料点上的帐户火焰传播，密度变化的前面，和流体动力学不稳定性。修改湍流扩散理论，将这些影响是具有挑战性的，因为理论是拉格朗日。在这篇文章中，我们提出了一个替代的欧拉框架的基础上的表面密度形式主义。我们采用所提出的框架来分析数据库的直接数值模拟的球形湍流预混火焰在衰减各向同性湍流和恢复机制的标度律提出和评估对数据。我们定量表征两种机制：一个有关的平均速度梯度引起的热膨胀和其他由于火焰传播中存在的曲率。我们表明，这两个过程的净效应是阻碍本配置中的湍流火焰刷的增长。我们的分析支持的概念，湍流火焰刷不会无限增长，而是达到最大厚度。
The thickness of the turbulent flame brush is central to the modeling of premixed turbulent combustion and the theory of turbulent diffusion is often applied to explain the growth of the brush with varying success. However, numerous studies have shown that the brush evolves differently from the dispersion of material points on the account of flame propagation, density changes across the front, and hydrodynamic instabilities. Modifications to turbulent diffusion theory to incorporate these effects are challenging since the theory is Lagrangian. In this article, we present an alternate Eulerian framework based on the surface density formalism. We employ the proposed framework to analyze a database of direct numerical simulations of spherical turbulent premixed flames in decaying isotropic turbulence and recover mechanisms for which scaling laws are proposed and assessed against data. We characterize quantitatively two mechanisms: one related to the mean velocity gradient induced by thermal expansion and the other due to flame propagation in the presence of curvature. We demonstrate that the net effect of these two processes is to hinder the growth of the turbulent flame brush in the present configuration. Our analysis supports the notion that the turbulent flame brush does not grow indefinitely, rather it attains a maximum thickness.