Numerical analyses for radiative autoignition and transition to flame spread over a vertically oriented solid fuel in a gravitational field

Pei Hsun Lin, Chiun-Hsun Chen

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

This study numerically investigates the ignition behaviors of vertically oriented cellulosic materials subjected to a radiant heat flux in a normal gravitational field. The entire process is delineated into two distinct stages. In the heating up stage, the maximum temperature increases with time but at a decreasing rate because of the pyrolysis reaction. The flame development stage consists of ignition and transition processes. In the ignition process, the maximum temperature in gas phase increases dramatically within a short period of time because a large amount of heat is generated from chemical reaction of the accumulative, flammable mixture. The flame is in a transition from a premixed flame to a diffusion one, except for the small region around the flame front. For the effect of varying the heating duration on ignition behavior, prolonging the imposed radiative heat time leads the ignition from a transition one to a persisting ignition. The effect of varying the solid fuel thickness indicates that the ignition delay time increases with an increase of solid fuel thickness while δs≤1.802. For 1.802≤δs≤3.244, the ignition delay times remain constant. Finally, if the external heating rate is the same order as the heat diffuse rate, the ignition delay time increases with an increase in solid fuel thickness.

Original languageEnglish
Pages (from-to)157-187
Number of pages31
JournalCombustion science and technology
Volume151
Issue number1
DOIs
StatePublished - 1 Jan 2000

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