Mathematical Modeling of Combustion Phenomena at the Microscale

Matalon0708588 该项目的目标是加强对微观尺度燃烧中发生的复杂过程的物理理解，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，这些方程由于不可避免的时间变化、多尺度过程和非平凡边界而进一步复杂化。 易处理的问题需要明智的建模努力，以捕捉正在考虑的现象的主要特征。 简化模型使用适当的分析或数值策略，以提供解决方案，使比较理论预测与实验观察。 这份研究报告提出了两组问题。 第一组是与预混燃烧在过剩焓燃烧室中的热燃烧产物的再循环，以加热新鲜的反应物，从而提高燃烧速率和热输出。 第二组问题是与非预混燃烧在一个封闭的槽，其中的混合区和所产生的扩散火焰蔓延在整个长度的reactorchannel。 目标是研究这种结构中火焰的结构、性质和动力学，并确定稳定燃烧、不稳定性发生、回火或吹出以及火焰熄灭的条件。 燃烧是一个备受经济和社会关注的课题。 尽管人们在不断地寻找替代能源，但燃烧仍然提供了今天消耗的大部分能源。 因此，重要的是要确保以最有效的方式利用燃烧过程，并以这种方式尽量减少对环境的不良影响。 近年来，由于对小规模和高密度能源的需求不断增加，以及碳氢燃料在单位质量的能量储存方面比电池具有巨大的优势，促使了微尺度能源领域的发展。 然而，为了使这项技术实用且高效，还需要解决一些重要问题。 除了与制造有关的困难之外，还需要克服与基本燃烧物理有关的基本问题。 微尺度燃烧系统的发展需要对微通道内流体流动、小尺度下的热质传递、小体积和复杂几何结构中的燃烧、壁面材料的热化学性质以及流体-壁面相互作用等基本问题有更深入的了解。 数学建模在实现这一目标中起着重要的作用，它提供了解释实验观测和确定这些观测的物理机制的方法。 这位研究者在他早期对流体力学和化学反应流的贡献的基础上，研究了微观尺度下燃烧的特殊性，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的影响.

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.