Experimental study of local extinction in laminar and turbulent flames

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1336184RenfroIn many practical combustors, heat is released by chemical reactions in relatively thin flame sheets. Turbulence in the flow of fuel and air in the combustor lead to fluctuations in velocity that perturb the flame sheet and increase the transfer of heat away from the flame. When these fluctuations are sufficiently large, the heat loss can be too high compared to the heat released by the flame resulting in local extinction. A local extinction event leaves a hole in the flame sheet that can lead to complete extinction of the flame. In many applications extinction is a significant limitation to the operation of the combustor, while in other applications extinction can be desired to quench a flame. In either case, physical understandings of the mechanisms that cause extinction are needed. This project seeks a fundamental understanding of the interactions of velocity and flame sheets that cause local extinction such that more accurate models of flame limits and the response of flame holes can be generated. The intellectual merit of the work focuses on a detailed understanding of the impact that velocity fluctuations in turbulent flames have on heat transfer from flames sheets as well as the impact of these changes to the flame's chemical heat release. The experimental and computational project will utilize an optically-accessible combustor that has been designed to create local extinction in a flame sheet enabling a detailed study using laser diagnostics. The measurements will be used to develop models describing extinction that can have broader impact on industrial design tools. The research will involve the participation of graduate and undergraduate students, who will be trained in fundamental combustion theory and application of optical measurements.