Experimental and Numerical Evaluation of Metallic Compounds for Suppressing Cup-Burner Flames

Published

June 1, 2004

Author(s)

Gregory T. Linteris, V Katta, F Takahashi

Abstract

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 less effective when evaluated in cup-burner flames. In order to understand the poor performance, the CO2 volume fraction required for extinction was 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. For Fe(CO)5 addition to the air stream at 450 mL/L, the peak scattering cross section for vertically polarized light was 1660 times the value for room temperature air. The first detailed numerical modeling studies were also performed for methane-air cup-burner flames with CO2 and Fe(CO)5 added to the oxidizer stream, and are used to interpret the experimental results. The role of particles was also illustrated by the numerical results, which showed that significant levels of super-saturation exist in the flame for several of the important iron-containing intermediates. This particle formation is favored in the lower temperature stabilization region of the cup-burner flames, as compared to the higher relevant temperatures of other flames. The results of this study indicate that the appropriate flame configuration for evaluating the effectiveness of some fire suppression agents must be carefully considered, since in those cases, different flame configurations can switch the relative performance of an agent by an order of magnitude.

Citation

Combustion and Flame

Volume

138

Issue

No. 1/2

Pub Type

Journals

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Keywords

cup burner, fire suppression, flame extinction, flame inhibition, flame stabilization, halon replacements, nano-particles, organometallic

Citation

Linteris, G. , Katta, V. and Takahashi, F. (2004), Experimental and Numerical Evaluation of Metallic Compounds for Suppressing Cup-Burner Flames, Combustion and Flame, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=861233 (Accessed April 25, 2024)