Simulations and Modeling of Turbulent Combustion Using Fuel Mixtures with High Hydrogen Content

固定式燃气轮机在目前的能源供应中扮演着重要的角色，它们在未来的能源格局中的重要性将继续增长，部分原因是它们具有良好的负载灵活性和快速启动能力。由于目前对可再生能源和更清洁地使用化石燃料的努力，燃气轮机的燃料灵活运行，特别是通过氢气浓缩燃料，正在成为基础研究和技术中的一个不断重要的主题。例如，在整体气化联合循环(IGCC)过程中使用氢气作为储能和燃烧合成气。然而，随着燃料中氢含量的增加，燃气轮机的稀燃燃烧特性发生了显著的变化。这可能会导致燃烧噪音增加、闪回、不必要的燃烧不稳定，并最终导致机器完全故障。在这里，特别是氢的差动扩散引起的热扩散不稳定性起着重要的作用，并可能导致火焰结构的强烈变化和局部熄灭区域。因此，本项目提案的主题是高含氢量燃料混合物的燃烧。其目标是实现基于计算机的燃烧室内湍流燃烧过程的模拟，考虑到燃料灵活操作的影响。如今，这样的模拟是燃气轮机开发和优化的重要组成部分。模拟的主要科学挑战之一是尚未充分了解火焰结构、差异扩散、热扩散不稳定性和湍流之间的复杂相互作用。在本项目中，应通过直接数值模拟(DNS)来研究这些现象。为此，将对不同氢含量的甲烷/氢混合物的预混湍流燃烧进行数值模拟。利用系统分析工具，将对所得数据进行先验和后验分析，以解决一些重要问题，例如关于火焰结构、燃烧速度和热扩散不稳定性对湍流的影响。工作假设是HHC燃料的燃烧可以用合适的多标量模型来描述。将在对域名系统数据进行系统分析的基础上，对所产生的未闭合术语进行适当的表述和建模。

Stationary gas turbines play a significant role in the present energy supply, and their importance will continue to grow in the energy landscape of the future, partly because of their good load flexibility and quick start capability. As a consequence of the present efforts for renewable energy and cleaner use of fossil fuels, fuel-flexible operation of gas turbines, and particularly fuel enrichment by hydrogen, is becoming an inceasingly important topic in fundamental research and technology. Examples include the use of hydrogen as energy storage and the combustion of syngas in the integrated gasification combined cycle (IGCC) process. However, the enrichment of fuels with high fractions of hydrogen results for lean stationary gas turbine combustion in a significant change in combustion characteristics. This can result in increased combustion noise, flashback, unwanted combustion instabilities, and eventually in complete machine failure. Here, especially thermo-diffusive instabilities, induced by differential diffusion of hydrogen, play an important role and can lead to strongly altered and cellular flame structures exhibiting locally extinguished regions. The topic of the present project proposal is therefore the combustion of fuel mixtures with high hydrogen content (HHC). The goal is to enable computer-based simulations of turbulent combustion processes in combustion chambers considering the effects found in fuel flexible operation. Such simulations nowadays are an important part of the development and optimization of gas turbines. One of the main scientific challenges for modeling is here that the complex interaction of flame structure, differential diffusion, thermo-diffusive instability, and turbulence is not yet sufficiently understood. Within this project, these phenomena shall be investigated by means of direct numerical simulations (DNS). For this, DNS will be performed for premixed turbulent combustion of methane/hydrogen mixtures with different hydrogen content. Using systematic analysis tools, the resulting data will be analyzed a priori and a posteriori to address some important questions, for example with respect to flame structure, burning rate, and the influence of thermo-diffusive instabilities on the turbulence. The working hypothesis is that the combustion of HHC fuels can be described by suitable multi-scalar models. An appropriate formulation and modeling of the resulting unclosed terms will be developed based on the systematic analysis of the DNS data.