Numerical Investigations of CO2 as Fire Suppressing Agent

Published

January 1, 2003

Author(s)

V Katta, F Takahashi, Gregory T. Linteris

Abstract

Understanding suppression mechanisms of different fire-suppressing agents including CF₃Br (Halon 1301) and inert gases is useful for their efficient use and for developing new agents. Because of the similarities between unsteady jet diffusion flames formed over the cup burner and uncontrolled fires, it is believed that studies of fire-suppressing agents in the former system could provide valuable information on the behavior of such agents in actual fires. In the present study, suppression characteristics of CO₂ were investigated in two flame systems: 1) a periodically oscillating, methane-air jet diffusion flame formed over a cup burner, and 2) a steady-state planar flame formed between opposing jets of fuel and air. A detailed chemical-kinetics model having 31 species and 346 elementary-reaction steps was used. Calculations made for the cup burner yielded a flame-flicker frequency of about 10 Hz. The suppression mechanisms promoted by CO2 were investigated by adding CO₂ to the airflow, while maintaining the total flow rate constant, for both the cup-burner and opposed-jet flames. In the cup-burner flame, the addition of CO₂ reduced the flame temperature to approximately equal to} 1620 K at suppression. Addition of CO₂ destabilized the flame base, which then moved downstream in search of a new stabilization location. For CO₂ volume fractions greater than 14.5 %, the flame base moved out of the computational area, as it could not find a stabilization point within this domain. The unsteady flickering motion of the flame and higher concentrations of CO₂ accelerated this quenching process through blowout. Even for very high concentrations of CO₂, the calculations did not yield simultaneous quenching of the entire cup-burner flame. On the other hand, the opposed-jet flame was extinguished through the global extinction of flame chemistry. The low-strain (30 s^-1) opposed-jet flame extinguished for CO₂ volume fractions > 16.4 %, while the moderately strained (90 s^-1) flame extinguished for volume fractions > 10.4 %. Both the opposed-jet flames extinguished nearly at the same flame temperature (approximately equal to} 1580 K), indicating that the extinction limits in these flames are primarily controlled by chemical kinetics.

Citation

7th International Symposium on Fire Safety Science

Pub Type

Journals

Keywords

cup burner, fire suppression, flame extinction, flame inhibition, halon replacement

Citation

Katta, V. , Takahashi, F. and Linteris, G. (2003), Numerical Investigations of CO₂ as Fire Suppressing Agent, 7th International Symposium on Fire Safety Science (Accessed April 23, 2024)