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.
