Suppression of High Speed Turbulent Flames in a Detonation/Deflagration Tube.
Suppression of High Speed Turbulent Flames in a
Detonation/Deflagration Tube.
(2811 K)
Gmurczyk, G. W.; Grosshandler, W. L.
NISTIR 5642; 55 p. January 1995.
Sponsor:
Naval Air Systems Command, Washington, DC
Available from:
National Technical Information Service
Order number: PB95-231817
Keywords:
turbulent flames; detonation; deflagration; halon 1301;
extinguishment; aircraft fires; combustion
Abstract:
Live-fire, full-scale testing has been conducted at
Wright-Patterson Air Force Base to identify an agent to
replace CF3Br (halon 1301) for suppressing fires in
military aircraft dry bays. The three chemicals being
considered (C2HF5, HFC-125, C3F8, FC-218, and CF3I,
halon 13001) had been evaluated in a previous laboratory
study, in which unique properties of each chemical were
identified in small-scale experiments. The CF3I
required the least mass to suppress a turbulent spray
flame but performed less-well in suppressing a
quasi-detonation. FC-218 performed the best in the
presence of a quasi-detonation. HFC-125 was recommended
previously as a candidate because of its superior
dispersion characteristics; however, this chemical
produced large over-pressures in the
detonation/deflagration tube. The high pressures
motivated the current study to determine the initial
conditions which would lead to dangerous conditions, and
to explore less extreme situations more representative
of a realistic threat. The detonation/deflagration tube
was lengthened from 7.5 to 10 m, the spiral insert in
the test section was removed, and the fuel was switched
from ethene to propane to produce uninhibited pressure
ratios below 9:1 and turbulent flame speeds between 300
and 600 m/s. The FC-218 provided the most consistent
performance in this new series of experiments which
examined lean, stoichiometric and rich initial
conditions. The CF3I had the greatest positive impact
at low concentrations, but exhibited non-monotonic
behavior of flame speed and shock pressure ratio at
increasing concentrations. Large pressure build ups
were not observed during suppression of the propane/air
mixtures under the current set of conditions. None of
the agents could be ruled out for dry bay applications
based upon the results of this study.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899