Extinction of Cup-Burner Diffusion Flames by Catalytic and Inert Inhibitors
Gregory T. Linteris
The first tests of super-effective flame inhibitors blended with CO2 have been performed in methane-air co-flow diffusion flames. Although the organometallic agents used are typically one or two orders of magnitude more effective inhibitors than CF3Br when evaluated in premixed and counterflow diffusion flames, they have been found to be surprisingly ineffective compared to CF3Br in cup-burner flames. In order to understand the poor performance, the CO2 volume fraction required for extinction was also determined for a range of added catalytic inhibitor volume fraction. When added at low volume fraction, the agents TMT, Fe(CO)5, and MMT, were effective at reducing the volume of CO2 required for extinction, with a performance relative to CF3Br of 2, 4, and 8, respectively. However, as the volume fraction of each metallic catalytic inhibitor was increased, the effectiveness diminished rapidly. The greatly reduced marginal effectiveness is believed to be caused by loss of active gas-phase species to condensed-phase particles. Laser scattering measurements in flames with Fe(CO)5 / CO2 blends detected particles both inside and outside (but not coincident with) the visible flame location. The peak scattering cross section for vertically polarized light was 220 times the value for room temperature air. For the metallic inhibitors, their effectiveness is believed to be reduced because of particle formation, followed by thermophoresis, which prevents the inhibiting species from reaching the relevant zone of the flame. The results indicate that the appropriate flame configuration for evaluating the effectiveness fire suppression agents can depend strongly upon properties of the agent itself, in some cases switching the measure of performance by an order of magnitude.
Proceedings of SEcond NRIFD Symposium: Science, Technolgy and Standards for Fire Suppression Systems
July 1-19, 2002
NRIFD Symposium-Science, Technology and Standards for Fire Suppression Systems
Extinction of Cup-Burner Diffusion Flames by Catalytic and Inert Inhibitors, Proceedings of SEcond NRIFD Symposium: Science, Technolgy and Standards for Fire Suppression Systems, Tokyo, JA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=861145
(Accessed December 3, 2023)