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Effects of Buoyancy on Lean Premixed V-Flames Part I: Laminar and Turblent Flame StructureLaser schlieren and planar laser-induced fluorescence techniques have been used to investigate laminar and turbulent v-flames in +g, -g, and micro g under flow conditions that span the regimes of momentum domination (Ri < 0. 1) and buoyancy domination (Ri > 0.1). Overall flame features shown by schlieren indicate that buoyancy dominates the entire flow field for conditions close to Ri = 1. With decreasing Ri, buoyancy effects are observed only in the far-field regions. Analyses of the mean flame angles demonstrate that laminar and turbulent flames do not have similar responses to buoyancy. Difference in the laminar +g and -g flame angles decrease with Ri (i.e., increasing Re) and converge to the microgravity flame angle at the momentum limit (Ri - 0). This is consistent with the notion that the effects of buoyancy diminish with increasing flow momentum. The +g and -g turbulent flame angles, however, do not converge at Ri = 0. As shown by OH-PLIF images, the inconsistency in +g and -g turbulent flame angles is associated with the differences in flame wrinkles. Turbulent flame wrinkles evolve more slowly in +g than in -g. The difference in flame wrinkle structures, however, cannot be explained in terms of buoyancy effects on flame instability mechanisms. It seems to be associated with the field effects of buoyancy that stretches the turbulent flame brushes in +g and compresses the flame brush in -g. Flame wrinkling offers a mechanism through which the flame responds to the field effects of buoyancy despite increasing flow momentum. These observations point to the need to include both upstream and downstream contributions in theoretical analysis of flame turbulence interactions.
Document ID
20000032152
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Cheng, Robert K.
(California Univ., Lawrence Berkeley Lab. Berkeley, CA United States)
Bedat, Benoit
(California Univ., Lawrence Berkeley Lab. Berkeley, CA United States)
Kostiuk, Larry W.
(Alberta Univ. Edmonton, Alberta Canada)
Date Acquired
August 19, 2013
Publication Date
January 1, 1998
Publication Information
Publication: Combustion and Flame
Publisher: Elsevier Science Inc.
Volume: 116
ISSN: 0010-2180
Subject Category
Inorganic, Organic And Physical Chemistry
Funding Number(s)
OTHER: DE-AC03-76F0-0098
CONTRACT_GRANT: NAS3-2000
Distribution Limits
Public
Copyright
Other

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