Mathematical Modeling of Combustion Phenomena at the Microscale

该项目的目标是加强对微观尺度上发生的复杂燃烧过程的物理理解，以支持和指导该领域正在进行的实验工作。在数学上，这些问题需要找到耦合的、高度非线性的偏微分方程的解，不可避免的时间变化、多尺度过程和非琐细的边界进一步复杂化。可处理的问题需要明智的建模努力，以便捕捉所考虑的现象的主要特征。使用适当的分析或数值策略来解决简化模型，以便提供能够将理论预测与实验观测进行比较的解决方案。调查者研究了两组问题。第一套是在超焓燃烧器中预混燃烧，热燃烧产物再循环加热新鲜反应物，从而提高燃烧速度和热量输出。第二组问题与密闭槽内的非预混燃烧有关，其中混合区和由此产生的扩散火焰蔓延到整个反应器通道的长度。目标是研究这种结构下火焰的结构、性质和动力学，并确定稳定燃烧、不稳定开始、闪回或吹灭以及火焰熄灭的条件。燃烧是一个巨大的经济和社会关注的主题。尽管人们一直在寻找替代能源，但燃烧仍然提供了今天消耗的大部分能源。因此，确保以最有效的方式利用燃烧过程，并以这种方式将对环境的不良影响降至最低，这一点非常重要。微尺度燃烧领域的最新发展是由于对小尺度和高密度电源的需求增加，以及碳氢化合物燃料在单位质量能量储存方面比电池具有巨大优势。然而，为了使这项技术实用和有效，还需要解决一些重要的问题。除了与制造相关的困难之外，还需要克服与潜在燃烧物理有关的基本问题。微尺度燃烧系统的发展需要在微通道流体流动的基础水平上有更深入的了解，小尺度的热量和质量传递，小体积和复杂几何形状的燃烧，壁面材料的热学和化学性质，以及流体-壁面相互作用。数学建模在实现这一目标方面发挥着重要作用；它提供了解释实验观察和确定负责这些观察的物理机制的方法。这位研究者在他早期对流体力学和化学反应流动的贡献的基础上，在微观尺度上研究燃烧的特性，以提高对这些现象的物理理解。通过指导和支持正在进行的实验工作，该项目对这项新技术的进步产生了直接影响。

Matalon0708588 The objective of the project is to enhance physicalunderstanding of the intricate processes occurring in combustionat the microscale, in order to support and guide ongoingexperimental efforts in this area. Mathematically, the problemsrequire finding solutions to coupled, highly nonlinear partialdifferential equations, further complicated by inevitabletemporal variations, multi-scale processes, and nontrivialboundaries. Tractable problems require judicious modelingefforts in order to capture the main features of the phenomenaunder consideration. The simplified models are addressed usingappropriate analytical or numerical strategies in order toprovide solutions that enable comparing the theoreticalpredictions with experimental observations. The investigatorexamines two sets of problems. The first set is associated withpremixed combustion in an excess-enthalpy combustor where the hotcombustion products are recirculated to heat up the freshreactants, thus enhancing the burning rate and heat output. Thesecond set of problems is associated with nonpremixed combustionin a confined slot, where the mixing zone and the resultingdiffusion flame spread over the entire length of the reactorchannel. The goal is to study the structure, properties anddynamics of flames in such configurations and identify conditionsfor steady burning, onset of instabilities, flashback or blowoff,and flame extinguishment. Combustion is a subject of great economical and societalconcern. Despite the continuing search for alternative energysources, combustion still provides the majority of the energyconsumed today. It is therefore important to ensure thatcombustion processes are utilized in the most efficient way, andin such a way as to minimize undesirable effects on theenvironment. Recent development in the field of microscalecombustion has been motivated by the increased need for smallerscale and high density power sources and by the fact thathydrocarbon fuels have enormous advantages over batteries interms of energy storage per unit mass. There are, however,important issues that need to be addressed in order to renderthis technology practical and efficient. Beyond the difficultiesassociated with fabrication, fundamental questions concerned withthe underlying combustion physics need to be overcome. Thedevelopment of combustion systems at the microscale requiresdeeper understanding at the fundamental level of fluid flow inmicrochannels, heat and mass transport at the small scale,combustion in small volumes and complex geometries, thermal andchemical properties of the wall materials, and fluid-wallinteractions. Mathematical modeling plays an important roletowards this goal; it provides means to explain experimentalobservations and identify the physical mechanisms responsible forthese observations. The investigator, building on his earliercontributions to fluid mechanics and chemically reacting flows,studies the peculiarities of combustion at the microscale inorder to improve physical understanding of these phenomena. Byguiding and supporting the ongoing experimental efforts theproject has an immediate effect on advancements of this newtechnology.