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Effect of gravity on the stability and structure of lean hydrogen-air flamesDetailed, time-dependent, 2D numerical simulations with full hydrogen-oxygen chemistry are used to investigate the effects of gravity on the stability and structure of laminar flames in lean, premixed hydrogen-air mixtures. The calculations show that the effects of gravity becomes more important as the lean flammability limit is approached. In a 12 percent hydrogen-air mixture, gravity plays only a secondary role in determining the multidimensional structure of the flame with the stability and structure of the flame controlled primarily by the thermo-diffusive instability mechanism. However, in leaner hydrogen-air mixtures gravity becomes more important. Upward-propagating flames are highly curved and evolve into a bubble rising upwards in the tube. Downward-propagating flames are flat or even oscillate between structures with concave and convex curvatures. The zero-gravity flame shows only cellular structures. Cellular structures which are present in zero gravity can be suppressed by the effect of buoyancy for mixtures leaner than 11 percent hydrogen. These observations are explained on the basis of an interaction between the processes leading to buoyancy-induced Rayleigh-Taylor instability and the thermo-diffusive instability.
Document ID
19920033984
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Patnaik, G.
(Naval Research Lab. Washington, DC, United States)
Kailasanath, K.
(U.S. Navy, Naval Research Laboratory, Washington DC, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1991
Subject Category
Propellants And Fuels
Meeting Information
Meeting: International Symposium on Combustion
Location: Orleans
Country: France
Start Date: July 22, 1990
End Date: July 27, 1990
Accession Number
92A16608
Distribution Limits
Public
Copyright
Other

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