Transition From Localized Ignition to Flame Spread Over a Thin Cellulosic Material in Microgravity.
Transition From Localized Ignition to Flame Spread Over
a Thin Cellulosic Material in Microgravity.
McGrattan, K. B.; Nakabe, K.; Baum, H. R.; Kashiwagi, T.
Combustion Institute/Eastern States Section. Chemical
and Physical Processes in Combustion. Technical
Meeting, 1993. October 25-27, 1993, Princeton, NJ,
409-412 pp, 1993.
Sponsor:National Aeronautics and Space Administration,
combustion; microgravity; ignition; flame spread;
cellulosic materials; vapor phases
Ignition and flame spread processes are complicated by
strong coupling between chemical reactions and transport
processes, not only in the gas phase but also in the
condensed phase. In most previous studies, ignition and
flame spread were studied separately with the result
that there has been little understanding of the
transition from ignition to flame spread. In fire
safety applications this transition is crucial to
determine whether a fire will be limited to a localized,
temporary burn or whether it will grow to become a large
fire. In order to understand the transition to flame
spread, the transient mechanisms of ignition and
subsequent spread must be studied. However, there have
been no definitive experimental or modeling studies
because of the complexity of the buoyancy-induced flow
near the heated sample surface. One must solve the full
Navier-Stokes equations over an extended region to
represent accurately the highly unstable buoyant plume
and entrainment of surrounding gas. To avoid the
complicated nature of the plume problem under normal
gravity, previous detailed radiative ignition models
were assumed to be one-dimensional or were applied at a
stagnation point. Unfortunately, these models could not
be extended to include the transition to flame spread.