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首页> 外文会议>US Combustion Meeting; 20070325-28; San Diego,CA(US) >Large-Eddy Simulation/Probability Density Function Formulation for Turbulent Spray Combustion
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Large-Eddy Simulation/Probability Density Function Formulation for Turbulent Spray Combustion

机译：湍流喷雾燃烧的大涡模拟/概率密度函数公式

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摘要

Turbulent combustion models often employ mixture fraction as a conserved scalar to map reactive scalars. While this approach has been successful in single-phase systems, several modeling hurdles appear in spray combustion. First, single-phase models presume the nature of the combustion regime allowing simplified combustion models to be constructed. However, spray combustion inherently consists of multiple combustion regimes and a rich variety of flame propagation mechanisms. Additionally, mixture fraction is no longer conserved due to the evaporative addition of fuel to the gas-phase. This mass addition alters the sub-grid statistical nature of the scalar. Consequently, the sub-grid probability density function (PDF) of mixture fraction cannot be reasonably approximated by a beta-function. To overcome these issues, a transported-PDF approach is formulated in the context of large-eddy simulation (LES) for spray combustion. In this approach, the sub-grid PDF of the scalars are directly solved for and need not be presumed. To ensure practical use, the joint-PDF transport equation for multicompo-nent fuel droplets is developed. This equation is high-dimensional and cannot be solved using Eulerian discretization methods. A consistent Lagrangian Monte-Carlo approach is formulated and coupled to the LES solver while maintaining temporal-accuracy. The coupled LES/PDF algorithm is then used to simulate a droplet-laden shear layer.
机译：湍流燃烧模型通常采用混合分数作为守恒标量来映射反应性标量。尽管这种方法在单相系统中很成功，但在喷雾燃烧中出现了一些建模障碍。首先，单相模型假定燃烧状态的性质，从而允许构造简化的燃烧模型。但是，喷雾燃烧固有地由多种燃烧方式和多种火焰传播机制组成。另外，由于将燃料蒸发添加到气相中，不再保留混合物分数。这种质量相加会更改标量的子网格统计性质。因此，混合分数的子网格概率密度函数（PDF）不能通过β函数合理地近似。为了克服这些问题，在大涡模拟（LES）的背景下制定了运输PDF方法以进行喷雾燃烧。在这种方法中，直接解决了标量的子网格PDF，并且无需假定。为了确保实际使用，开发了用于多组分燃油滴的联合PDF传输方程。该方程是高维的，无法使用欧拉离散化方法求解。制定了一致的拉格朗日蒙特卡罗方法，并与LES解算器耦合，同时保持了时间精度。然后，使用耦合的LES / PDF算法来模拟载有液滴的剪切层。

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  • 来源
  • 会议地点 San DiegoCA(US)
  • 作者

    V. Raman; O. Desjardins;

  • 作者单位

    Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin, Austin, Texas 78712, USA;

    Department of Mechanical Engineering, Stanford University, Stanford, California 98305, USA;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 理论;
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