The stabilization and extinction of a microjet diffusion flame

Krishnan, Gautham

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https://hdl.handle.net/2142/105690 Copy

Description

Title

The stabilization and extinction of a microjet diffusion flame

Author(s)

Krishnan, Gautham

Issue Date

2019-07-16

Director of Research (if dissertation) or Advisor (if thesis)

Matalon, Moshe

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(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.

Graduation Semester

2019-08

Type of Resource

text

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http://hdl.handle.net/2142/105690

Copyright and License Information

Copyright 2019 Gautham Krishnan

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