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The Diffusion Flame in Free Convection. Buoyancy-induced Flows, Oscillations, Radiative Balance, and Large-scale Limiting Rates.

Authors
Hertzberg-M; Cashdollar-KL; Litton-CD; Burgess-DS
Source
NTIS: PB 277 250 :33 pages
Link
NIOSHTIC No.
10000427
Abstract
This Bureau of Mines report describes experimental and theoretical studies of diffusion flames in free convection. The cross-coupling between buoyancy-induced flows and the combustion process is explored as it relates to the size, structure, and radiative balance of flames. New data are presented for the size-dependent radiance oscillations of diffusion flames and for the angular distribution of the total radiant intensity from a small methanol pool flame. Both amplitude and frequency of the measured oscillations are compared with theoretical predictions that are based on a new view of the structure of diffusion flames. This new view, which is at variance with the traditional one, assumes uniform reaction in the diffusive mixing zone, and recognizes the significance of the role played by convective buoyancy and its duality in both aiding and impeding flame propagation. Buoyancy quenches propagation at low burning velocities, introducing a real discontinuity in the combustion rate. A "flammable volume" is thus defined as that bound between lean- and rich-limit contours. However, in the flow disturbances generated by combustion waves that consume that volume, buoyancy aids propagation by promoting the convective mixing of a new flammable volume. The measured radiance oscillations are manifestations of these propagation and remixing cycles.
Publication Date
19780101
Document Type
IH; Report of Investigations
Fiscal Year
1978
NTIS Accession No.
PB-277250
NTIS Price
A04
Identifying No.
RI 8263
NIOSH Division
PRC;
Source Name
NTIS: PB 277 250
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