Agent Screening for Halon 1301 Aviation Replacement.
Agent Screening for Halon 1301 Aviation Replacement.
(793 K)
Grosshandler, W. L.; Gann, R. G.; Hamins, A.; Nyden, M.
R.; Pitts, W. M.; Yang, J. C.; Zachariah, M. R.
U.S. Environmental Protection Agency, Environment Canada
and United National Environmental Program.
International CFC and Halon Alternatives Conference,
1993. Stratospheric Ozone Protection for the 90's.
October 20-22, 1993, Washington, DC, 744-752 pp, 1993.
Keywords:
halons; ozone; halon 1301; thermal properties;
dispersions; fluid mechanics; flame extinguishment;
flammable materials; pressure vessels
Abstract:
A comprehensive experimental program is described in
which eleven gaseous agents and sodium bicarbonate
powder have been screened, so that the best three
candidates for subsequent full-scale aircraft fire
extinguishment evaluation can be identified. Chemicals
with both a low ozone depletion potential and a high
fire suppression efficiency were sought. Because the
effectiveness of a fire suppression agent is known to be
related to its thermodynamic properties, its behavior
during two-phase flow, its interaction with flame
chemistry, the timing of its release and the nature of
the fire, a series of carefully designed experiments was
conducted to examine each of these factors. Theoretical
models were used to interpret the results, to increase
our understanding of the suppression process, and to
predict behavior over an expanded range of operating
conditions. A pressure vessel with a rupture disc was
used to discharge the agent into the atmosphere. Nine
pure fluorocarbons, two mono-chlorinated fluorocarbons,
a fluorocarbon azeotrope, and sodium bicarbonate powder
were tested mixed with nitrogen or CF3H. The existing
jet was photographed and laser light extinction was used
to determine the extent and velocity of the jet. Four
different type flame measurements were used to
characterize suppression effectiveness. A description
of the various flame screens is presented here.
Chemical kinetics and molecular dynamic modeling were
used as a means to investigate the extinction mechanism
and to identify alternative gaseous chemicals likely to
be superior to the original list of eleven.
