Ignition Suppression by CF 3 Br and CF 3 I of HzIOzIAr Mixtures : Detailed Studies of Time and Space Resolved Radical Profiles

Introduction While steady progress continues toward the goal of finding halon replacements, the urgency of the problem has led to empirical searches which often neglect, out of necessity, the fundamental physics and chemistry of fire suppression and inhibition. Although a variety of halon replacements is or soon will be commercially available, their performance in terms of fire suppression is typically a factor of two worse than that of the halons they replace. The requirements for the halon replacements are smngent and often conflicting: high fire suppression performance, low toxicity, low reactivity and environmental acceptability. Two of these performance requirements, fire suppression and environmental acceptability, are particularly difficult since the same halogen radicals that catalytically inhibit combustion also catalytically destroy stratospheric ozone. Since strict regulations now drive environmental compliance, it is not surprising that a significant research effort has been devoted to elucidating the environmental issues of stratospheric ozone depletion and global warming, and that thus fire suppression performance might have to be sacrificed for environmental compliance. In order to achieve simultaneously fire suppression performance greater or equal to the halons and environmental acceptability, we will need an understanding of fire suppression that rivals the detailed chemical and physical knowledgebase developed for the problem of stratospheric ozone depletion. A complete understanding of fire suppression and inhibition will require a wide range of investigations. Both theoretical and experimental studies are needed to develop chemical reaction mechanisms, to measure missing reaction rates, to develop models coupling chemistry and gas dynamics, and to validate these models through carefully designed experiments. Here we seek to address primarily this last point. In contrast to ozone depletion, fire suppression is in some ways easier to study since realistic model scenarios can be studied under controlled, laboratory conditions. In recent years, a great deal of effort has been expended to develop flame diagnostic techniques to probe in detail the physics and chemistry of combustion. In particular, laser based diagnostics offer the ability to