The use of halons for fire fighting is being phased out due to their deleterious effects on stratospheric ozone. This paper describes the findings of part of a study designed to characterize and identify super-effective thermal fire-fighting agents as possible replacements for these effective compounds. A full report describing the study is available. [ ] Thermal agents refer to compounds that act simply by extracting heat from a flame zone and lowering the temperature to a point where combustion can no longer be sustained. These types of agents should be contrasted with chemical agents that generate active chemical species (e.g., the bromine atoms generated by halons) that interfere with the radical chain branching mechanisms required to sustain combustion.During the 2001 Joint National Meeting of the United States Section of the Combustion Institute experimental measurements of extinguishing concentrations for nitrogen, argon, helium and carbon dioxide for opposed-flow (Tsuji burner) and coflow (Santoro burner) diffusion flames of methane and propane were described. [ ] Briefly, these studies showed that the amount of a thermal agent required to extinguish a given flame depended on the type of burner, the fuel, and the thermal agent. The highest volume fractions of a given thermal agent were required for opposed-flow porous burner flames with the coflowing flame requiring approximately 65 % as much. Methane flames were easier to extinguish than propane flames, requiring roughly 25 % less agent. The relative effectiveness of the agents was ordered as CO2 > N2 . He > Ar. The higher effectiveness of helium compared to argon is particularly interesting since these two inert gases have identical heat capacities and, if heat absorption were the sole controlling property, would be expected to require the same volume fractions for extinguishment.In this paper the results of detailed chemical modeling calculations designed to provide a better understand of the experimental observations and to test the ability of such models for predicting extinguishing concentrations of thermal agents for methane and propane diffusion flames are described.
December 2-5, 2001
Technical Meeting of the Eastern States Section of the Combustion Institute
burners, databases, diffusion flames, fire extinguising agents, fire suppressants, fire suppression, laminar flames, reaction kinetics, surface cooling