Micro-mixing in Turbulent Flames: Perspective and Model Development Using Direct Numerical Simulation

燃烧质量的好坏决定了能源生产装置的排放性能。但燃烧过程很大程度上依赖于燃料和空气的混合。与燃烧相关的尺度上的混合通常被称为微观混合。湍流火焰中的反应物混合速率受流体动力学、分子扩散和热释放的控制。此外，这些过程彼此之间是强耦合的。目前描述混合现象的数学模型是基于我们对零放热量等简单情况的理解。激光对湍流火焰的诊断研究表明，放热和密度波动对混合过程有重要影响。首席研究员和他的同事最近的理论分析证实了这一实验观察。在这个项目中，我们的目标是通过直接的数值模拟来加深对湍流火焰中微观混合过程的理解。从直接模拟中获得的有关微观混合过程的信息将与悉尼火焰进行比较。由此获得的深入知识将被转化为数学模型，该模型可以很容易地并入工业CFD代码中。本项目的预期结果是验证了S模型，该模型严格基于湍流火焰中微观混合的基本守恒方程。

The quality of combustion determines the emission performance of energy producing devices. But the combustion process depends strongly on the mixing of fuel and air. The mixing at scales relevant for the combustion is commonly called as micro-mixing. The reactant mixing rate in turbulent flames is governed by the fluid dynamics, the molecular diffusion, and the heat release. Also, these processes are strongly coupled to one another. The current mathematical models describing the mixing phenomenon are based on our understanding of simple situations like zero heat release. Recent laser diagnostic studies of turbulent flames show the important influences of heat release and density fluctuation on the mixing process. Recent theoretical analysis by the principal investigator and his co--worker corroborates this experimental observation. In this project, we aim to develop a deep understanding on the micro-mixing process in turbulent flames by conducting direct numerical simulations. The information on the micro--mixing processes obtained from the direct simulation will be compared to Sydney Flames. The deep knowledge gained thus will be translated into a mathematical model which can be easily incorporated into industrial CFD codes. The expected outcome of this project is validated model(s) which are rigorously based on the fundamental conservation equation for the micro-mixing in turbulent flames.