Direct and large Eddy simulation of turbulent premixed combustion

这项拟议的研究是利用大涡和直接数值模拟(LES和DNS)来研究湍流预混燃烧。预混燃烧发生在燃料和氧化剂在燃烧之前混合，然后燃烧的特点是局部湍流火焰速度的变化，这使得系统建模变得困难。它被用于从用于发电的固定式燃气轮机到火花点火内燃机的应用。它在稀薄预混燃烧中尤其重要，这是一种减少排放的新方法，但它可能导致燃烧不稳定。损坏发动机或导致关闭。由于火焰的局部行为和整个燃烧过程都受湍流-火焰相互作用的细节控制，因此需要对这些相互作用有更好的理解和建模能力。这里的总体目标是：1.从本质上更好地了解预混火焰-湍流相互作用，以及2.最终开发能够模拟燃气轮机燃烧室内燃烧的LES代码。在这项工作中将使用DNS和LES。该DNS从整体上求解反应流的控制方程，不需要建模。它包括了湍流的所有尺度，因此计算非常密集--拟议的研究涉及使用升级的Sharcnet设备来观察在SI发动机和大型燃气轮机中常见的区域中的简单火焰的部分。此外，将使用DNS运行的结果，不仅用于观察火焰与湍流的相互作用，而且帮助开发大型涡旋模拟的模型。DILES解决了流动中的大部分湍流；然而，与大涡模拟不同的是，它不计算湍流的最小尺度，然后必须对这些小尺度的“亚网格尺度”特征进行建模。由此产生的大涡模拟能够同时考虑真实燃烧室的高雷诺数和复杂的几何形状，同时仍然包括真实的火焰湍流行为。

The proposed research is on the use of Large Eddy and Direct Numerical Simulations (LES and DNS) to study turbulent premixed combustion.  Premixed combustion occurs where the fuel and oxidiser are mixed before they are burnt, and the combustion is then characterised by a locally varying turbulent flame speed which makes modelling the system difficult.  It is used in applications ranging from stationary gas turbines used for power generation to spark ignition IC engines.  It is particularly important in lean premixed combustion, a new approach to reducing emissions, but one that can lead to combution instabilities, damaging engines or causing shutdowns.  Both the local behaviour of the flames and the overall combustion process are controlled by the details of the turbulence-flame interactions, so a better understanding and modelling capability of these interactions are required.  The overall objectives here are to:   1. gain an inherently better understanding of premixed flame-turbulence interactions, and   2. ultimately develop an LES code capable of simulating the combustion within gas turbine combustors Both DNS and LES will be used in this work.  DNS solves the governing equations of the reacting flow in their entirety with no modelling required. It includes all of the scales of the turbulence and is consequently very computationally intensive -the proposed research involves using the upgraded Sharcnet facilities to look at parts of simple flames in regimes commonly seen in SI engines and large-scale gas turbines.  The results of the DNS runs will be used, not only to look at flame-turbulence interactions, but also to help develop models for the large eddy simulations.  LES resolves most of the turbulence in the flow; however, unlike DNS, it does not calculate the smallest scales of the turbulence and these small-scale "subgrid scale" features must then be modelled.  The resulting LES is then able to consider both the high Reynolds numbers and the complex geometries of real combustors while still including the real flame-turbulence behaviour.