Citation

Funashima K, Iizuka H, Kuwana K, Kushida G. J. Combust. Soc. Jpn. 2019; 61(197): 250-257.

Copyright

(Copyright © 2019, Combustion Society of Japan)

DOI

10.20619/jcombsj.1901

PMID

unavailable

Abstract

Near-limit flame spread is a topic of extensive fire research, and recent studies pointed out that near-limit flame spread characteristics were significantly affected by flame instability. This study considers opposed-flow flame spread in a narrow channel, in which oxygen supply by natural convection is suppressed, leading to near-limit conditions. Fingering instability appears when the oxidizer flow velocity or the channel height is small. A major objective of this study is to numerically examine the influence of fingering instability on the flame spread velocity and the extinction limit. Three-dimensional basic equations are first developed and then reduced to two-dimensional ones considering the narrowness of the domain. Numerical solutions of the two-dimensional model, in particular, fingering patterns and flame spread velocities are compared with previous experimental data, and reasonable agreement between them is confirmed. Traveling wave solutions for one-dimensional basic equations are then obtained and compared with the corresponding two-dimensional solutions. It is found that the two-dimensional flame spread velocity is faster than the one-dimensional value because the reaction is enhanced by instability. It is also found that two-dimensional flame spread is possible under certain conditions for which extinction occurs in one-dimensional flame spread. Dependence of flame spread velocity and extinction limit on model parameters is finally discussed based on predictions of the one-dimensional model.

Language: ja

Keywords

Fingering instability; Flame spread; Narrow channel; Numerical simulation; Traveling wave solution