Suppression of a Non-Premixed Flame Behind a Step.
Suppression of a Non-Premixed Flame Behind a Step.
(367 K)
Grosshandler, W. L.; Hamins, A.; McGrattan, K. B.;
Charagundla, S. R.; Presser, C.
Combustion Institute, Symposium (International) on
Combustion, 28th. Proceedings. Volume 2. July
20-August 4, 2000, Edinburgh, Scotland, Combustion
Institute, Pittsburgh, PA, Candel, S.; Driscoll, J. F.;
Burgess, A. R.; Gore, J. P., Editor(s)(s), 2957-2964 pp,
2000.
Keywords:
combustion; fire suppression; simulation; halon 1301;
premixed flames; pool fires; experiments
Abstract:
Because of its many positive attributes, halon 1301, or
trifluorobromomethane (CF3Br), has been used as a fire
extinguishing agent in many applications, including
aircraft, ships, and specialized structures. Due to its
high ozone depletion potential, however, world-wide
production was halted in 1994. In the search for a
long-range replacement, novel types of extinguishing
agents and delivery mechanisms are under development. To
gauge the suitability of a replacement agent, methods
are needed to evaluate the material's suppression
effectiveness under conditions that relate to field
applications. In this study, a laboratory-scale facility
has been developed to screen the suppression
effectiveness of agents that are delivered in a
transient fashion, such as solid propellant, gas
generators. The facility features a pool fire stabilized
behind an obstruction, which is known to be a highly
challenging suppression configuration. The character of
the flame and the impact of the air flow, propane flow,
obstruction geometry, and rate of agent addition on the
amount of material needed for suppression are examined
for N2 and CF3Br. The impact of the injection process
on the flowfield and the transport of the agent
downstream are examined. A simple mixing model is useful
to explain the observed trend of decreasing suppressant
mass fraction with increasing injection duration, even
for agents as different as CF3Br and N2. Direct
numerical simulation of the suppression event is shown
to successfully predict the quantity and rate of N2
required to extinguish the flame based upon a published
global reaction rate for premixed propane/air flame
propagation.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899