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Title:The stabilization and extinction of a microjet diffusion flame
Author(s):Krishnan, Gautham
Advisor(s):Matalon, Moshe
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Jet diffusion micro-flames
Extinction limit
Burke-Schumann flame
Large activation-energy asymptotics
Abstract:The steady jet diffusion micro-flame is mathematically modeled and its extinction properties and investigated in this study. The diffusion flame of interest is one that results from the reaction of a fuel present in a weak jet issuing from a nozzle into an unbounded medium containing the oxidizer. Various flame properties such as flame location, temperature and reactant leakage are investigated in the study. The analysis presented makes use of an asymptotic approximation for large activation energy chemical reactions as per the general theory of Cheatham and Matalon where the reaction is confined to a surface and the mathematical problem reduces to a free boundary problem with jump relations across the flame sheet. Constant density approximation decouples the hydrodynamic equations from the full system of governing equations. The flow field is described by an exact solution to the Navier-Stokes and continuity equations modeling an axis-symmetric jet issuing from a point source of momentum into an unbounded fluid domain, as solved for by both Landau and Squire. The flame location and associated combustion fields are first solved in the Burke-Schumann limit of complete combustion for unity Lewis number flames in jets of arbitrary strength. The solution is then attempted for the case of non-unity Lewis number Burke-Schumann flames in weak jets (micro-jets). Finally, the solution associated with non-unity Lewis number micro-flames with reactant leakage across the flame is investigated over the entire range of Damkohler numbers in order to ascertain extinction properties. Effects of varying the Lewis and Damkohler numbers on extinction and flame shape are presented.
Issue Date:2019-07-16
Rights Information:Copyright 2019 Gautham Krishnan
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08

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