- Author
-
Nakabe, K.
|
McGrattan, K. B.
|
Kashiwagi, T.
|
Baum, H. R.
|
Yamashita, H.
|
Kushida, G.
- Title
- Ignition and Transition to Flame Spread Over a Thermally Thin Cellulosic Sheet in a Microgravity Environment.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Journal
-
Combustion and Flame,
Vol. 93,
No. 4,
361-374,
1994
- Sponsor
- National Aeronautics and Space Administration, Lewis Research Center, Cleveland, OH
- Contract
- NASA-GRANT-C-32000-4
- Keywords
-
microgravity
|
ignition
|
flame spread
|
oxygen
|
autoignition
|
cellulose
|
oxygen concentration
- Abstract
- An axisymmetric, time-dependent model is developed describing auto-ignition and subsequent transition to flame spread over a thermally-thin cellulosic sheet heated by external radiation in a quiescent microgravity environment. Due to the unique combination of a microgravity environment and low Reynolds number associated with the slow, thermally induced flow, the resulting velocity is taken as a potential flow. A one-step global gas phase oxidation reaction and three global degradation reactions for the condensed phase are used in the model. A maximum external radiant flux of 5 W/cm² (Gaussian distribution) with 21%, 30%, and 50% oxygen concentrations is used in the calculations. The results indicate that autoignition is observed for 30% oxygen concentrations but the transition to the flame spread does not occur. For 50% oxygen the transition is achieved. A detailed discussion of the transition from ignition to flame spread is given as an aid to understanding this process. Also, a comparison is made between the axisymmetric configuration and a two-dimensional (line source) configuration.