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.
Proceedings Title: International CFC and Halon Alternatives Conference
Conference Dates: October 20-22, 1993
Conference Location: Washington, DC
Pub Type: Conferences
halons, ozone, halon 1301, thermal properties, dispersions, fluid mechanics, flame extinguishment, flammable materials, pressure vessels