Numerical Modeling of Non-Premixed Flame-Wall Interactions in Turbulent Boundary Layer Flows

获奖摘要建议书编号：CTS-0553508首席研究员：Trouve，Arnaud C.机构：马里兰州大学园区提案标题：湍流边界层流动中非预混火焰-壁面相互作用的数值模拟火焰-壁面相互作用（FWI）在许多燃烧系统中起着重要作用。例如，在内燃机中，冷却壁与短火焰壁距离的出现相结合导致火焰淬灭，并且FWI在热效率和污染倾向方面对发动机性能具有负面影响。在航空推进和发电应用中也观察到类似的效果，特别是考虑到最近的趋势是设计更紧凑、更小（中尺度或微尺度）的燃烧室;相关的更高的表面积与体积比和更短的火焰壁距离导致火焰壁相互作用对燃烧系统性能的更大影响。封闭空间火灾是FWI发挥重要作用的另一个燃烧主题。例如，垂直可燃壁的燃烧是一种普通的配置，其中燃料在浮力驱动的壁边界层内释放和消耗，并且整个燃烧过程可以被认为是FWI。在冷壁面附近，火焰强度因局部淬火而降低，而气固热通量在火焰接触处达到峰值。尽管有这些发现，然而，FWI现象仍然被忽视的工程级计算流体动力学（CFD）工具，有必要适应近似壁边界条件用于描述湍流边界层的发生FWI。本项目的总体目标是响应这一需求，并扩展当前壁层模型的能力，以描述火焰-壁面相互作用。该项目的范围集中在浮力驱动的非预混火焰与惰性或易燃墙壁的相互作用，这是火灾应用中发现的一个常见问题。本文的主要研究内容包括：基于直接数值模拟的火焰-壁面相互作用的详细研究;基于大涡模拟的火焰-壁面相互作用的详细研究;基于壁面分层的火焰-壁面相互作用的详细研究;壁面分层模型的开发;第一模型验证组件，其基于用建模的或解析的壁层执行的LES模拟之间的比较;在这第二个验证组件中，选定的实验配置对应于Ahmad Faeth研究的经典湍流垂直壁火灾实验。总之，本项目的智力价值包括推进知识，并提高模拟能力，FWI配置感兴趣的火灾应用。预计拟议的工作也将为与发动机应用相关的类似开发铺平道路。更广泛的影响包括使用现代计算工具，为开发急需的基于工程（基于性能）的消防安全方法做出贡献。该项目也有一个教育部分，解决了以下问题：需要在计算火灾建模领域教育合格的劳动力;需要通过为BS学生提供研究经验来加强本科教育;需要通过开发一个新的研究生级计算火灾建模课程来开发跨学科的工程课程。

Award AbstractProposal Number: CTS-0553508Principal Investigator: Trouve, Arnaud C.Institution: University of Maryland College ParkProposal Title: Numerical Modeling of Non-Premixed Flame-Wall Interactons in Turbulent Boundary Layer Flows Flame-wall interactions (FWI) play an important role in many combustion systems. For instance in Internal Combustion engines, cooled walls combined with occurrences of short flame-wall distances result in flame quenching and FWI has a negative impact on engine performance, both in terms of thermal efficiency and pollution propensity. Similar effects are observed in aeronautical propulsion and power-generation applications, especially given the recent trends towards the design of more compact, smaller (meso- or micro-scale) combustion chambers; the associated higher surface-to-volume ratios and shorter flame-wall distances result in a larger impact of flame-wall interactions on the combustion system performance. Enclosure fires are another combustion topic in which FWI plays an important role. For instance, the burning of a vertical flammable wall is a generic configuration where the fuel is released and consumed within the buoyancy-driven wall boundary layer and the entire combustion process may be considered as FWI.FWI phenomena are found to result in significant changes in the flame and wall dynamics: the flame strength is reduced near cold wall surfaces by local quenching events while the gas-solid heat flux takes peak values at flame contact. Despite these findings, however, FWI phenomena remain neglected in engineering-level Computational Fluid Dynamics (CFD) tools and there is a need to adapt the approximate wall boundary conditions used to describe turbulent boundary layers to the occurrence of FWI. The general objective of the present project is to respond to that need and extend the capabilities of current wall-layer models to the description of flame-wall interactions. The scope of the project is focused on interactions of buoyancy-driven non-premixed flames with inert or flammable walls, a generic problem found in fire applications. The modeling effort is developed in the framework of a large eddy simulation (LES) approach.The main components of the proposed research program are: a detailed study of flame-wall interactions based on direct numerical simulations; a detailed study of flame-wall interactions using LES with resolved wall layers; a model development component aimed at adapting wall-layer models to the treatment of FWI; a first model validation component based on a comparison between LES simulations performed with modeled or resolved wall layers; a second model validation component based on a comparison between LES simulations and experimental data. In this second validation component, the selected experimental configuration corresponds to the classical turbulent vertical wall fire experiment studied by Ahmad & Faeth.In summary, the intellectual merit of the present project includes advancing knowledge in, and enhancing simulation capabilities for, FWI configurations of interest to fire applications. The proposed work is also expected to pave the way for similar developments relevant to engine applications. The broader impacts include a contribution to the development of a much-needed engineering-based (performance-based) approach to fire safety using modern computational tools. The project has also an educational component that addresses the following issues: the need to educate a qualified work force in the area of computational fire modeling; the need to enhance Undergraduate education by providing a research experience to BS students; the need to develop an interdisciplinary engineering curriculum through the development of a new Graduate-level computational fire modeling class.