Numerical Modeling of Flame Propagation in the Flamelet Regime

小火焰状态下火焰传播的数值模拟

• 批准号: 0552140
• 负责人: Moshe Matalon
• 金额: $ 24万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-15 至 2007-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0552140&HistoricalAwards=false
• 关键词: Numerical; Modeling; Flame; Propagation; Flamelet

Award AbstractProposal Number: CTS-0552140Principal Investigator: Matalon, MosheInstitution: Northwestern University Proposal Title: Numerical Modeling of Flame Propagation in the Flamelet RegimeCombustion is a subject of great economical and societal concern. Despite the continuing search for alternative energy sources, combustion still provides the majority of the energy consumed today. It is therefore important to ensure that combustion processes are utilized in the most efficient way and in such a way as to minimize undesirable effects on the environment. The proposed activity is directed towards improving our understanding of combustion phenomena, which may consequently lead to suggestions for better engineering design. The specific objective is to model and simulate complex flame propagation problems similar to the one encountered in practical applications. Predictions based on such models may lead to improvement in the efficiency of combustion devices, saving in fuel consumption, and reduction in the emission of pollutants and unwanted after-burning products. The broader impact of the proposed work will occur through publications and presentations in the technical and scientific community and by training and educating a new generation of scientists for careers in academia and industry. Combustion problems encompass the interaction of phenomena that take place on different time and length scales. Resolving such problems on all scales, small and large, poses a mathematically challenging and computationally intensive task. It is proposed to numerically simulate complex flame propagation problems by exploiting their multi-scale nature. The asymptotic advances in flame theory will be used to simplify the mathematical description. With the flame confined to a surface, the mathematical formulation reduces to a free-boundary problem supplemented by conditions that account for the influences of the processes occurring on the smaller scales. The simplified problem, still nonlinear, is quite challenging; but its relative simplicity enables addressing the dynamics of large-scale multi-dimensional flames while spanning a wide range of the physical parameters. For the description of some of the problems proposed in this project, the hydrodynamic model in its present state is adequate. The model incorporates effects of thermal expansion, differential and preferential diffusion, mixture strength, non-unity reaction orders, temperature-dependent transport and volumetric heat losses (radiative losses), and can potentially include detailed kinetics using reduced chemistry mechanisms. Using this framework, it is proposed to numerically simulate the nonlinear development of hydrodynamically unstable flames, flame wrinkling and flame acceleration, and the effect of external random noise on the propagation. Occasionally, the hydrodynamic description needs to be modified, for example by allowing for the creation of holes along the flame surface and its consequences. The proposed work has many potential applications including turbulent flames, particularly in the flamelet regime, where the smallest relevant scales are larger than the flame thickness and therefore do not affect the internal flame structure. Such regime encompasses many practical applications, for example spark-ignition engines and turbojets.

奖励摘要标志：CTS-0552140原理研究员：Mosheinstitution Matalon：西北大学提案标题：火焰状况中火焰传播的数值建模是巨大的经济和社会问题的主题。尽管持续寻找替代能源，但燃烧仍然提供了当今消耗的大部分能源。因此，重要的是要确保以最有效的方式使用燃烧过程，并以最小化对环境的不良影响的方式。提出的活动旨在提高我们对燃烧现象的理解，因此可能会为更好的工程设计提出建议。具体的目标是建模和模拟与实际应用中遇到的相似的复杂火焰传播问题。基于此类模型的预测可能会提高燃烧设备的效率，节省燃料消耗以及减少污染物和不必要的后燃烧产品的排放。拟议工作的更广泛影响将通过技术和科学界的出版物和演讲发生，并通过培训和教育新一代科学家从事学术界和工业的职业。燃烧问题涵盖了在不同时间和长度尺度上发生的现象的相互作用。在大小规模上解决此类问题，构成了数学上具有挑战性和计算密集的任务。提议通过利用其多尺度性质来数字模拟复杂的火焰传播问题。火焰理论中的渐近进步将用于简化数学描述。随着火焰局限于表面，数学公式将其减少到一个自由边界问题，该问题被解释了发生在较小尺度上的过程的条件。简化的问题（仍然是非线性）非常具有挑战性。但是它的相对简单性可以解决大规模多维火焰的动态，同时跨越了广泛的物理参数。为了描述该项目中提出的一些问题，目前状态的流体动力模型就足够了。该模型结合了热膨胀，差异和优先扩散，混合强度，非合成反应顺序，依赖温度的转运和体积热量损失（辐射损失）的影响，并且可以使用降低的化学机制来可能包括详细的动力学。使用此框架，建议通过数值模拟流体动力学不稳定的火焰，火焰皱纹和火焰加速度的非线性发展，以及外部随机噪声对传播的影响。有时，需要修改流体动力学描述，例如，允许沿火焰表面及其后果创建孔。提出的工作具有许多潜在的应用，包括湍流火焰，尤其是在火焰状态下，其中最小的相关尺度大于火焰厚度，因此不会影响内部火焰结构。这种政权包括许多实际应用，例如火花点燃引擎和涡轮喷气机。