Ignition and Transition to Flame Spread Over a Thermally Thin Cellulosic Sheet in a Microgravity Environment.
Ignition and Transition to Flame Spread Over a Thermally
Thin Cellulosic Sheet in a Microgravity Environment.
Nakabe, K.; McGrattan, K. B.; Kashiwagi, T.; Baum, H.
R.; Yamashita, H.; Kushida, G.
Combustion and Flame, Vol. 93, No. 4, 361-374, 1994.
Sponsor:National Aeronautics and Space Administration, Lewis
Research Center, Cleveland, OH
microgravity; ignition; flame spread; oxygen;
autoignition; cellulose; oxygen concentration
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.