EAGER: Experimental investigation of physical-space scalar structure and unresolved mixing to improve large-eddy simulation of turbulent combustion

EAGER：物理空间标量结构和未解决的混合的实验研究，以改进湍流燃烧的大涡模拟

• 批准号: 2208136
• 负责人: Chenning Tong
• 金额: $ 29.68万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2208136&HistoricalAwards=false
• 关键词: EAGER; Experimental; investigation; physical; space

This project investigates a key process, turbulent mixing, in combustion. Turbulent combustion occurs and plays an important role in many engineering applications, such as jet engines, gas turbine generators, internal combustion engines, and chemical processing plants. The modern design process of such devices needs to employ numerical modeling to evaluate design choices and to optimize design parameters. However, the current state-of-the art modeling approach, large-eddy simulation (LES), despite decades of research efforts, still does not have the accuracy needed for advanced engineering design, primarily because the unresolved mixing process is not well predicted. Previous efforts to understand mixing had been partially hampered by the predominant LES approach. This research will investigate mixing using the novel LES approach developed by S. B. Pope as the framework, which overcomes the limitations of the traditional approach. The new approach, however, also poses challenges in experimental techniques and data analysis methods. The researchers will employ a new laser diagnostic technique and new statistical analysis method. The research will significantly advance the understanding of the fundamental physics in turbulent combustion, which will potentially enable development of combustion models with sufficient accuracy for designing high-performance and low emission engineering devices, which will have a positive impact on society and the environment. The understanding of the physics gained will also benefit other research areas involving interactions between turbulence and strongly nonlinear phenomena, such as chemical engineering processes, atmospheric physics, atmospheric chemistry, and environment systems.This project investigates the physical-space structure and the unresolved mixing as well as their interaction with chemistry using the recently developed self-conditioned fields LES approach (Pope 2010) as the framework, which overcomes the limitations of the filtering LES approach. The researchers will conduct experiments in turbulent non-reactive coaxial jets and in jet flames. Two-dimensional images will be obtained in coaxial jets. A new photo-dissociation-based diagnostic technique and new statistical analysis method will be used. Direct numerical simulation of a Sydney flame (Thorsten et al. 2019), which contains 3D images, will complement the experiments. Researchers will analyze the physical-space scalar structure and its representation in the self-conditioned joint PDF and the unclosed mixing terms in its transport equation. The results provide a basis for investigating the mixing of mixture fraction and temperature in piloted turbulent partially premixed (Sandia) flames. The researchers will analyze the effects of the physical-space scalar structure on the self-conditioned scalar JMDF and the unclosed mixing terms. The project is the first to use the novel self-conditioned LES approach as the framework. It is also the first time true two-dimensional images of mixture fraction and temperature with resolved dissipation scales are obtained in turbulent hydrocarbon flames without major compromising assumptions. The results are expected to significantly advance the understanding of the unresolved physics essential for developing improved mixing models capable of accurately predicting multiscalar mixing and turbulence-chemistry interaction.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目研究燃烧中的一个关键过程——湍流混合。湍流燃烧在许多工程应用中发生并发挥着重要作用，例如喷气发动机、燃气涡轮发电机、内燃机和化学加工厂。此类设备的现代设计过程需要采用数值建模来评估设计选择并优化设计参数。然而，当前最先进的建模方法——大涡模拟（LES），尽管经过了数十年的研究努力，仍然不具备先进工程设计所需的精度，主要是因为未解决的混合过程没有得到很好的预测。先前理解混合的努力部分受到主要 LES 方法的阻碍。本研究将使用 S. B. Pope 开发的新颖 LES 方法作为框架来研究混合，该方法克服了传统方法的局限性。然而，新方法也对实验技术和数据分析方法提出了挑战。研究人员将采用新的激光诊断技术和新的统计分析方法。该研究将显着增进对湍流燃烧基础物理的理解，这将有可能开发出具有足够精度的燃烧模型，以设计高性能和低排放的工程设备，这将对社会和环境产生积极影响。对物理的理解也将有益于涉及湍流和强非线性现象之间相互作用的其他研究领域，例如化学工程过程、大气物理、大气化学和环境系统。该项目研究物理空间结构和未解决的混合以及它们与化学的相互作用，使用最近开发的自调节场 LES 方法（Pope 2010）作为框架，克服了过滤 LES 方法的局限性。研究人员将在湍流非反应同轴射流和射流火焰中进行实验。二维图像将在同轴喷射中获得。将使用新的基于光解离的诊断技术和新的统计分析方法。悉尼火焰的直接数值模拟（Thorsten et al. 2019）包含 3D 图像，将补充实验。研究人员将分析物理空间标量结构及其在自条件联合 PDF 中的表示及其输运方程中的未封闭混合项。结果为研究先导湍流部分预混（桑迪亚）火焰中混合分数和温度的混合提供了基础。研究人员将分析物理空间标量结构对自条件标量 JMDF 和未封闭混合项的影响。该项目是第一个使用新颖的自调节 LES 方法作为框架的项目。这也是第一次在湍流碳氢化合物火焰中获得具有解析耗散尺度的混合分数和温度的真实二维图像，而无需做出重大妥协的假设。研究结果预计将显着促进对未解决物理问题的理解，这对于开发能够准确预测多标量混合和湍流化学相互作用的改进混合模型至关重要。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力评估进行评估，被认为值得支持。优点和更广泛的影响审查标准。