Flamelet based chemical reduction techniques are very promising methods for efficient and accurate modeling of premixed flames. Over the years the Flamelet Generated Manifold (FGM) technique has been developed by the Combustion Technology Group of Eindhoven University of Technology. Current state-of-the-art of FGM for the modeling of premixed and partially-premixed flames is reviewed. The fundamental basis of FGM consists of a generalized description of the flame front in a (possibly moving) flame-adapted coordinate system. The basic nature of the generalized flamelet model is that effects of strong stretch in turbulent flames are taken into account by resolving the detailed structure of flame stretch and curvature inside the flame front. The generalized flamelet model, which forms the basis on which FGM is built, is derived in Part I. To be able to validate numerical results of flames obtained with full chemistry and obtained from FGM, it is important that the generalized flamelet model is analyzed further. This is done by investigating the impact of strong stretch, curvature and preferential diffusion effects on the flame dynamics as described by the local mass burning rate. This so-called strong stretch theory is derived and analyzed in Part I, as well as multiple simplifications of it, to compare the strong stretch theory with existing stretch theories. The results compare well with numerical results for flames with thin reaction layers, but described by multiple-species transport and chemistry. This opens the way to use the generalized flamelet model as a firm basis for applying FGM in strongly stretched laminar and turbulent flames in Part II. The complete FGM model is derived first and the use of FGM in practice is reviewed. The FGM model is then validated by studying effects of flame stretch, heat loss, and changes in elements, as well as NO formation. The application to direct numerical simulations of turbulent flames is subsequently studied and validated using the strong stretch theory. It is shown that the generalized flamelet model still holds even in case of strong stretch and curvature effects, at least as long as the reaction layer is dominated by reaction and diffusion phenomena and not perturbed too much by stretch related perturbations. The FGM model then still performs very well with a low number of control variables. Turbulent flames with strong preferential diffusion effects can also be modeled efficiently with an FGM model using a single additional control variable for the changes in element mass fractions and enthalpy. Finally FGM is applied to the modeling of turbulent flames using LES and RANS flow solvers. For these cases, the flame front structure is not resolved anymore and unresolved terms need to be modeled. A common approach to include unresolved turbulent fluctuations is the presumed probability density function (PDF) approach. The validity of this FGM-PDF approach is discussed for a few test cases with increasing level of complexity.

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使用火焰生成的歧管进行预混燃烧建模的最新技术

基于火焰的化学还原技术是对预混火焰进行有效和准确建模的非常有前途的方法。多年来，埃因霍温理工大学燃烧技术小组开发了 Flamelet 生成歧管 (FGM) 技术。回顾了用于预混和部分预混火焰建模的 FGM 的最新技术水平。FGM 的基本基础包括在（可能是移动的）火焰适应坐标系中对火焰前沿的广义描述。广义小火焰模型的基本性质是通过解析火焰前沿内部的火焰拉伸和曲率的详细结构来考虑湍流火焰中强拉伸的影响。广义小火焰模型是构建 FGM 的基础，在第 I 部分中导出。为了能够验证通过完整化学获得的火焰的数值结果和从 FGM 获得的火焰，重要的是进一步分析广义火焰模型。这是通过研究强拉伸、曲率和优先扩散效应对局部质量燃烧速率所描述的火焰动力学的影响来完成的。第一部分推导和分析了这种所谓的强拉伸理论，并对其进行了多次简化，以将强拉伸理论与现有的拉伸理论进行比较。结果与具有薄反应层的火焰的数值结果相比很好，但由多物种传输和化学描述。这开辟了使用广义火焰模型作为在第二部分中在强烈拉伸的层流和湍流火焰中应用 FGM 的坚实基础的方法。首先导出完整的 FGM 模型，并回顾 FGM 在实践中的使用。然后通过研究火焰拉伸、热损失和元素变化以及 NO 形成的影响来验证 FGM 模型。随后使用强拉伸理论研究和验证了湍流火焰直接数值模拟的应用。结果表明，即使在强拉伸和曲率效应的情况下，广义小火焰模型仍然适用，至少只要反应层由反应和扩散现象主导，并且不会受到与拉伸相关的扰动过多的扰动。FGM 模型在控制变量数量较少的情况下仍然表现良好。具有强优先扩散效应的湍流火焰也可以使用 FGM 模型有效地建模，使用单个附加控制变量来控制元素质量分数和焓的变化。最后，使用 LES 和 RANS 流求解器将 FGM 应用于湍流火焰的建模。对于这些情况，不再解析火焰前沿结构，需要对未解析的项进行建模。包含未解决的湍流波动的常用方法是假定概率密度函数 (PDF) 方法。讨论了这种 FGM-PDF 方法的有效性，用于一些复杂程度不断增加的测试用例。火焰前沿结构不再解析，未解析项需要建模。包含未解决的湍流波动的常用方法是假定概率密度函数 (PDF) 方法。讨论了这种 FGM-PDF 方法的有效性，用于一些复杂程度不断增加的测试用例。火焰前沿结构不再解析，未解析项需要建模。包含未解决的湍流波动的常用方法是假定概率密度函数 (PDF) 方法。讨论了这种 FGM-PDF 方法的有效性，用于一些复杂程度不断增加的测试用例。