A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames

Walsh, Kevin T. and Fielding, Joseph and Smooke, Mitchell D. and Long, Marshall B. and Liñán Martínez, Amable (2005). A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames. "Proceedings of the Combustion Institute", v. 30 (n. 1); pp. 2547-2555. ISSN 1540-7489.

Description

Title: A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames
Author/s:
  • Walsh, Kevin T.
  • Fielding, Joseph
  • Smooke, Mitchell D.
  • Long, Marshall B.
  • Liñán Martínez, Amable
Item Type: Article
Título de Revista/Publicación: Proceedings of the Combustion Institute
Date: January 2005
ISSN: 1540-7489
Volume: 30
Subjects:
Freetext Keywords: Coflow diffusion flames; Diagnostics; Modeling; Reduced gravity; Composition; Diffusion; Fuels; Gravitation; Mathematical models; Mixtures; Turbulent flow; Laminar diffusion flames; Flame research
Faculty: E.T.S.I. Aeronáuticos (UPM)
Department: Motopropulsión y Termofluidodinámica [hasta 2014]
Creative Commons Licenses: Recognition - Non commercial

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Abstract

As a sensitive marker of changes in flame structure, the number densities of excited-state CH (denoted CH*), and excited-state OH (denoted OH*) are imaged in coflow laminar diffusion flames. Measurements are made both in normal gravity and on the NASA KC-135 reduced-gravity aircraft. The spatial distribution of these radicals provides information about flame structure and lift-off heights that can be directly compared with computational predictions. Measurements and computations are compared over a range of buoyancy and fuel dilution levels. Results indicate that the lift-off heights and flame shapes predicted by the computations are in excellent agreement with measurement for both normal gravity (1g) and reduced gravity flames at low dilution levels. As the fuel mixture is increasingly diluted, however, the 1g lift-off heights become underpredicted. This trend continues until the computations predict stable flames at highly dilute fuel mixtures beyond the 1g experimental blow-off limit. To better understand this behavior, an analysis was performed, which indicates that the lift-off height is sensitive to the laminar flame speed of the corresponding premixed mixture at the flame edge. By varying the rates of two key "flame speed" controlling reactions, we were able to modify the predicted lift-off heights so as to be in closer agreement with the experiments. The results indicate that reaction sets that work well in low dilution systems may need to be modified to accommodate high dilution flames.

More information

Item ID: 939
DC Identifier: http://oa.upm.es/939/
OAI Identifier: oai:oa.upm.es:939
Deposited by: Archivo Digital UPM
Deposited on: 04 Apr 2008
Last Modified: 20 Apr 2016 06:36
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