Citation

Pagni PJ. Fire Safety J. 1981; 3(4): 273-285.

Copyright

(Copyright © 1981, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Nine classic diffusion flames, i.e., combustion systems with initially separate fuel and oxidizer, are synthesized in a search for common dimensionless parameters which may serve as indice of fire hazard. The problems examined are: planar and cylindrical Burke-Schumann; droplet burning; planar and cylindrical stagnant film; and forced, free, mixed, and stagnation point combusting boundary layers. Similarity solutions in pyrolysis regions permit identification of flame locations and quantification of excess pyrolyzate, i.e., fuel which is not consumed locally. Numerical solutions in downstream regions give explicit expressions for flame extensions in terms of the number and the B number, with the former dominating. This key parameter, the physically available oxygen-to-fuel ratio divided by the chemically required oxygen-to-fuel ratio or inverse equivalence r ratio, emerges as indicative of the fire hazard associated with flame extension. Full scale tests have shown that flame extension is related to fire spread beyond the compartment of origin. Small r means large flame. Polystyrene with r = 0.12, for example, has an order of magnitude longer flame than wood with r = 0.6. Other polymers fall between these extremes. Much progress remains to be made in the areas of flame soot, radiation, turbulence, and compartment interactions.