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Suppression of High-Speed C2H4/Air Flames With C1-Halocarbons.


pdf icon Suppression of High-Speed C2H4/Air Flames With C1-Halocarbons. (643 K)
Gmurczyk, G. W.; Grosshandler, W. L.

Combustion Institute, Symposium (International) on Combustion, 25th. Proceedings. July 31-August 5, 1994, Irvine, CA, Combustion Institute, Pittsburgh, PA, 1497-1503 pp, 1994.

Keywords:

fire suppression; predictive models; halons; halon 1301; shock waves; turbulent flames; flame extinguishment; dynamic characteristics

Abstract:

Experimental investigations of the effect of the presence of five C1-halocarbons (CF4, CHF3, CF3I, CHF2Cl and CF3Br) on the suppression of premixed high-speed turbulent flames and quasi-detonations have been carried out in a 7.5 m long, 50 mm diameter tube. Lean and Stoichiometric C2H4/air mixtures initially at 100 kPa and 295 K and in the absence of any halocarbon constituted the reference state. A primary objective of the work has been to determine the relative suppression efficiencies of different agents under highly dynamic situations, without the undue influence of either the ignition event or the mixing of the agent into the flame front. This was accomplished by generating a highly turbulent flame/quasi-detonation in the driver section, which contained no suppressant, followed by measurements of the velocity and pressure ratio as the wave front entered the test section of the tube, which contained suppressant premixed with the same fuel/air combination. A turbulence generator in the form of a spiral obstruction was used in the tube to broaden the gas dynamic conditions attainable by the flame. Flame and shock wave velocities up to 1300 m/s, pressure ratios across the shock fronts over 26:1, and shock wave/flame spacings of the order of 10 cm were measured with piezo-electric pressure transducers and fast photodiodes. The experimental facility was successfully employed to clearly discriminate among the dynamic characteristics of the five compounds, revealing behavior distinct from what was observed in companion studies using atmospheric non-premixed flames. The suppression process is strongly influenced by the concentration of an agent, the structure and composition of an agent molecule, and the composition of the combustible mixture itself.