US-UK Cooperative Science: Modeling and Simulation of Two- Dimensional Flames in Turbulent Flows

该奖项将支持美国和英国机械工程师之间为期三年的合作研究项目，该项目的主题是湍流中二维火焰的建模和模拟。美国调查人员米切尔·斯穆克博士和马歇尔·朗博士都来自耶鲁大学，他们将与英国剑桥大学工程系的K·布雷教授和B·罗格博士合作开展这项工作。研究人员建议研究二维燃烧系统中火焰曲率和部分预混的影响。到目前为止，使用层流火焰面概念模拟非预混湍流燃烧的几何模型过于简单，因为它们不能反映湍流火焰中瞬时局部熄灭的重要原因。因此，它们不太可能提供对真实过程的自信数值预测所需的精细化程度，例如柴油机燃烧室中的湍流燃烧，其中自动点火和火焰传播发生在高温和高压下。拟议的工作计划将涵盖三个具体领域：1)识别和制定层流火焰片几何形状的二维模型，从而能够可靠地预测曲率对火焰片结构的影响和部分预混合对火焰片传播的影响。2)对现有的二维轴对称层流扩散火焰的数值算法和自适应网格方法进行了改进，并将其应用于本生尖端和三点火焰等问题的研究。3)对预混和非预混构型进行了一系列实验和计算(包括详细的输运和有限速率化学)，并对采用层流火焰面概念的湍流燃烧模型的数据进行了评估和解释。拟议的工作将对采用层流火焰面概念的湍流模型、污染物形成和排放控制产生直接影响。该研究计划将受益于美国和英国小组在燃烧建模和先进计算方面的综合专业知识。

This award will support a three year cooperative research project between U.S. and British mechanical engineers on the topic of modeling and simulation of two-dimensional flames in turbulent flows. The U.S. investigators, Dr. Mitchell Smooke and Dr. Marshall Long, both from Yale University, will collaborate in this work with Professor K. Bray and Dr. B. Rogg, Department of Engineering, Cambridge University, England. The investigators propose to examine the effects of flame curvature and partial premixing in two-dimensional combustion systems. Until now the geometries employed in modeling both nonpremixed turbulent combustion using the laminar flamelet concept have been too simple in the sense that they have been unable to reflect the important causes of instantaneous local extinction in a turbulent flame. As a result, they are unlikely to provide the degree of refinement necessary for confident numerical predictions of realistic processes such as turbulent combustion in the chamber of a Diesel engine where auto- ignition and flame propagation occur at high temperatures and pressures. The proposed work program will cover three specific areas: 1) Identification and formulation of two-dimensional models of laminar flamelet geometries that allow confident predictions of the effects of curvature on the flamelet structure an the effects of partial premixing on flamelet propagation. 2) Modification of existing numerical algorithms and adaptive gridding procedures that have been developed for two-dimensional axisymmetric laminar diffusion flames with the goal of applying them to the study of problems such as the Bunsen tip and the triple point flame. 3) Implementation of a series of experiments and calculations (with detailed transport and finite rate chemistry) for both premixed and nonpremixed configurations with subsequent evaluation and interpre- tation of the data with respect to turbulent combustion models employing the laminar flamelet concept. The work proposed will have a direct impact on turbulence models employing the laminar flamelet concept, on pollutant formation and on emissions control. The research program will benefit from the combined expertise of the U.S. and British groups in combustion modeling and advanced computation.