Suppression of High-Speed C2H4/Air Flames With C1-Halocarbons.
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899