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Premixed Gas Combustion: An Excitable SystemRotating spiral and target patterns have been observed experimentally on freely-propagating premixed gas flames in large diameter tubes at normal gravity (1-g). These modes of propagation occur in near-limit mixtures which have a Lewis number (Le, defined as the ratio of the thermal diffusivity of the cold mixture to the mass diffusivity of the scarce component into the mixture) sufficiently greater than one. However, at 1-g, buoyant flows strongly distort the flame curvature, hydrodynamics (thus stretch) and convective transport of species and heat. In turn, these alter the critical Le required for onset of instability. To isolate and better understand the mechanisms which drive the observed patterns and their dynamics, 1-g and microgravity (micro-g) experiments are being conducted to determine: (1) the structure and dynamics of the patterns, (2) a map of the critical Le and heat loss for their occurrence, (3) the relative significance of the chemical kinetics, and (4) the effect of curvature (local wave and global flame front) on wave propagation. With this in hand, we will be better prepared to discuss an additional mode, a state of 'chemical turbulence,' which seems to be the ultimate fate of many of these near-limit flames prior to extinction.
Document ID
19970020601
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Pearlman, Howard
(University of Southern California Los Angeles, CA United States)
Date Acquired
August 17, 2013
Publication Date
May 1, 1997
Publication Information
Publication: Fourth International Microgravity Combustion Workshop
Subject Category
Inorganic And Physical Chemistry
Accession Number
97N21874
Funding Number(s)
CONTRACT_GRANT: NCC3-501
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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