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Title: The interaction of high-speed turbulence with flames: Global properties and internal flame structure

Abstract

We study the dynamics and properties of a turbulent flame, formed in the presence of subsonic, high-speed, homogeneous, isotropic Kolmogorov-type turbulence in an unconfined system. Direct numerical simulations are performed with Athena-RFX, a massively parallel, fully compressible, high-order, dimensionally unsplit, reactive flow code. A simplified reaction-diffusion model represents a stoichiometric H{sub 2}-air mixture. The system being modeled represents turbulent combustion with the Damkoehler number Da=0.05 and with the turbulent velocity at the energy injection scale 30 times larger than the laminar flame speed. The simulations show that flame interaction with high-speed turbulence forms a steadily propagating turbulent flame with a flame brush width approximately twice the energy injection scale and a speed four times the laminar flame speed. A method for reconstructing the internal flame structure is described and used to show that the turbulent flame consists of tightly folded flamelets. The reaction zone structure of these is virtually identical to that of the planar laminar flame, while the preheat zone is broadened by approximately a factor of two. Consequently, the system evolution represents turbulent combustion in the thin reaction zone regime. The turbulent cascade fails to penetrate the internal flame structure, and thus the action of small-scale turbulence ismore » suppressed throughout most of the flame. Finally, our results suggest that for stoichiometric H{sub 2}-air mixtures, any substantial flame broadening by the action of turbulence cannot be expected in all subsonic regimes. (author)« less

Authors:
;  [1]
  1. Laboratory for Computational Physics and Fluid Dynamics, Naval Research Laboratory, Washington, DC 20375 (United States)
Publication Date:
OSTI Identifier:
21305717
Resource Type:
Journal Article
Journal Name:
Combustion and Flame
Additional Journal Information:
Journal Volume: 157; Journal Issue: 5; Other Information: Elsevier Ltd. All rights reserved; Journal ID: ISSN 0010-2180
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LAMINAR FLAMES; COMBUSTION; HYDROGEN; VELOCITY; TURBULENCE; AIR; COMPUTERIZED SIMULATION; MIXTURES; FLAME PROPAGATION; ZONES; STOICHIOMETRY; WIDTH; DIFFUSION; TIME DEPENDENCE; COMBUSTION KINETICS; Turbulent premixed combustion; Flamelets; Flame structure

Citation Formats

Poludnenko, A Y, and Oran, E S. The interaction of high-speed turbulence with flames: Global properties and internal flame structure. United States: N. p., 2010. Web. doi:10.1016/J.COMBUSTFLAME.2009.11.018.
Poludnenko, A Y, & Oran, E S. The interaction of high-speed turbulence with flames: Global properties and internal flame structure. United States. https://doi.org/10.1016/J.COMBUSTFLAME.2009.11.018
Poludnenko, A Y, and Oran, E S. 2010. "The interaction of high-speed turbulence with flames: Global properties and internal flame structure". United States. https://doi.org/10.1016/J.COMBUSTFLAME.2009.11.018.
@article{osti_21305717,
title = {The interaction of high-speed turbulence with flames: Global properties and internal flame structure},
author = {Poludnenko, A Y and Oran, E S},
abstractNote = {We study the dynamics and properties of a turbulent flame, formed in the presence of subsonic, high-speed, homogeneous, isotropic Kolmogorov-type turbulence in an unconfined system. Direct numerical simulations are performed with Athena-RFX, a massively parallel, fully compressible, high-order, dimensionally unsplit, reactive flow code. A simplified reaction-diffusion model represents a stoichiometric H{sub 2}-air mixture. The system being modeled represents turbulent combustion with the Damkoehler number Da=0.05 and with the turbulent velocity at the energy injection scale 30 times larger than the laminar flame speed. The simulations show that flame interaction with high-speed turbulence forms a steadily propagating turbulent flame with a flame brush width approximately twice the energy injection scale and a speed four times the laminar flame speed. A method for reconstructing the internal flame structure is described and used to show that the turbulent flame consists of tightly folded flamelets. The reaction zone structure of these is virtually identical to that of the planar laminar flame, while the preheat zone is broadened by approximately a factor of two. Consequently, the system evolution represents turbulent combustion in the thin reaction zone regime. The turbulent cascade fails to penetrate the internal flame structure, and thus the action of small-scale turbulence is suppressed throughout most of the flame. Finally, our results suggest that for stoichiometric H{sub 2}-air mixtures, any substantial flame broadening by the action of turbulence cannot be expected in all subsonic regimes. (author)},
doi = {10.1016/J.COMBUSTFLAME.2009.11.018},
url = {https://www.osti.gov/biblio/21305717}, journal = {Combustion and Flame},
issn = {0010-2180},
number = 5,
volume = 157,
place = {United States},
year = {Sat May 15 00:00:00 EDT 2010},
month = {Sat May 15 00:00:00 EDT 2010}
}