Nonlinear Dynamics of Premixed and Diffusion Flames

Northwestern University, Evanston IL

Investigators

Abstract

0072588 Matalon The objective of the proposed work is to derive and analyze mathematical models that describe the dynamics of flames. The models will be derived systematically from the conservation laws of mass, momentum and energy by means of asymptotic methods and analyzed using analytical and numerical methods. It is proposed to identify mathematical models that contain enough details of the real combustion systems and analyze these models in order to gain basic understanding on how the physical and chemical processes interact in the simpler circumstances. Comparison with the experimental record will be performed in order to test the models and their predictions. The mathematical problems involve nonlinear evolution equations and nonlinear aspects of flame instabilities. The objective of the proposed work is to gain fundamental understanding in the complex processes occurring in combustion problems, problems that are encountered in various engineering applications. Improving our fundamental understanding of combustion phenomena could suggest new directions for applied research and lead to a better design of combustion systems. The problems that will be investigated are related to phenomena that have been observed in the laboratory but are not yet completely understood. The proposed work will address three classes of problems: The first class is concerned with the evolution of premixed flames in open space and in confined environments, where the coupled effects between the flame and the hydrodynamic field is of primary interest. Studies of premixed flames have significant technological importance and are directly applicable to internal combustion engines processes. The second class of problems is concerned with instabilities in non-premixed combustion, or diffusion flames, for which theoretical studies are only now emerging. Non-premixed conditions are favored in furnaces for safety reasons and in diesel engines here the liquid fuel evaporates in the combustion chamber providing the necessary fuel vapor that burns with air. The third class of problems is concerned with flame spread over flammable liquids, where the combined behaviors in the liquid and gas phases determine the flame dynamics. Flame spread over an accidental spillage of a flammable liquid, or a "running liquid fire" encountered in petrochemical industries, can become a fire hazard.