Numerical analyses for radiative ignition and transition to flame spread over a horizontally oriented solid fuel in a gravitation field

P. H. Lin, W. F. Fan, Chiun-Hsun Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

This study numerically investigates the ignition behaviors of horizontal-oriented cellulosic materials subjected to radiant heat flux under a natural convective environment. This process can be divided into two stages: (1) the heating-up stage, during which the maximum temperature increases with time and (2) the flame development stage, consisting of the ignition and transition processes. The ignition process is marked with a sharp increase in maximum temperature. Meanwhile, the flame is in a transition from a premixed flame into a diffused one. In the transition process, the flame propagates upstream, forming a so-called opposed flame spread. There is a time lag between solid fuel pyrolysis and the gas-phase chemical reaction. The pyrolysis front overtakes the flame front in the initial heating-up process. As soon as the flammable mixture ahead of the flame front is ignited, the flame moves forward quickly, moving ahead of the pyrolysis front. The ignition delay time is shorter for a horizontal solid fuel than for a vertical solid fuel under the same environment, because the resultant high-temperature region is not cooled and the flammable mixture is not diluted by the induced flow in a horizontal solid fuel. For the effect of changing gravity, the ignition delay time decreases with a decrease in gravity level, owing to the smaller induced flow velocity.

Original languageEnglish
Pages (from-to)47-74
Number of pages28
JournalCombustion science and technology
Volume173
Issue number1
DOIs
StatePublished - 1 Jan 2001

Keywords

  • Flame spread
  • Gravitational field
  • Horizontally oriented
  • Radiative ignition
  • Solid fuel

Fingerprint Dive into the research topics of 'Numerical analyses for radiative ignition and transition to flame spread over a horizontally oriented solid fuel in a gravitation field'. Together they form a unique fingerprint.

Cite this