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Suppression of High Speed Turbulent Flames in a Detonation/Deflagration Tube.


pdf icon 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.