In this study, the flame spread phenomena over a thermally thin solid fuel, with consideration of solid radiation, in a purely zero-gravitational field is studied numerically. A derivation of critical thickness for flame extinction including radiation effect is given. Parametric studies are carried out by varying the fuel thickness (τ̄) and ambient oxygen concentration (YO∞). Under a fixed ambient oxygen concentration, a dividing point is identified to distinguish the flame-spread rate into two regimes against the solid fuel thickness. In the regime of τ̄≤τ̄ dividing, the flame-spread rate decreases with the solid fuel thickness. The flame does not exist anymore when the solid fuel thickness is lower than a critical value. In the regime, τ̄>τ̄ dividing, the flame-spread rate gradually decreases as the solid fuel thickness increases. The controlling mechanisms in these two regimes are fuel control and heat transfer control, respectively. The flame is extinguished due to radiation loss as τ̄ is larger than a certain value, derived theoretically. The responses of solid fuel, including temperature, density, vaporized mass flux, conduction heat flux from flame to the solid fuel, solid-radiation heat flux and net heat flux, are presented as well. The flame-spread rate increases with the oxygen concentration. The predicted extinction limit is at YO∞=0.195. The standoff distance increases with a decrease of oxygen concentration. A comparison with corresponding experimental results in the literature is given. The agreements are quite well.
|Number of pages||11|
|Journal||Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao|
|State||Published - 1 Jun 2003|
- Flame spread
- Fuel thickness
- Oxygen concentration