Suppression of high speed flames and quasi-detonations

Past research has identified three candidates as near term replacements for CF,Br in some aircraft total-flooding fire protection applications: CF,I, C2HF, and C,F,. The behavior of these compounds when added to lean, stoichiometric and rich propanelair mixtures exposed to subsonic and supersonic combustion waves is examined using a 10 m long, 50 mm diameter detonatioddeflagration tube. Pressure and visible radiation are measured as a function of the amount of agent in the mixture to determine the pressure ratio across the incident shock wave and the speed of the radiation front. The results are compared to earlier studies using ethene, in which significantly higher pressure ratios and wave speeds were generated. The presence of the three extinguishing compounds in the propanelair mixtures causes the combustion either to be enhanced or suppressed, and depending upon the dynamical situation and the concentration of the agent, any of the three can outperform the others. For example, C,F, is the most effective compound for attenuating combustion systems for all stoichiometries; C2HF, reduces the threat by 90 % when its volume fraction is 11 %, the best performance of the three, but amplifies the severity of the deflagration the most at a volume fraction of 5 %; and the best agent for attenuating the pressure increase of the shock wave is CF,I under most conditions.