- Author
- Peters, J. W.
- Title
- Studies of Dry-Powder Extinguishment of Diffusion Flames for Condensed Fuels. Final Technical Report. June 15, 1982.
- Coporate
- Princeton Univ., Princeton, NJ
- Sponsor
- National Bureau of Standards, Gaithersburg, MD
- Report
- NBS GCR 82-412, November 1982, 123 p.
- Distribution
- Available from National Technical Information Service
- Contract
- NB81NADA2041
- Keywords
- aluminum oxides | diffusion flames | extinction | heptanes | liquid fuels | particle size | powders | oxygen concentration
- Abstract
- A powder deliver system for the extinction of diffusion flames of condensed fuels is studied. The main component of the delivery system is a glass elutriation vessel containing a bed of powder. The extinction experiments were conducted in counterflow flame geometry. A flat, laminar diffusion flame was produced in a stagnation-point boundary layer by directing an ocidizing gas stream downward onto the surface of a liquid fuel burning at atmospheric pressure. The flame could be extinguished by either decreasing the oxygen mass fraction in the oxidizer stream or increasing the velocity of the oxidizing gas stream. The mass ratio of powder to nitrogen plus powder was maintained at a number of different fixed values to generate extinction curves. The fundamental measurement taken was the oxygen mass fraction required for extinction as a function of the velocity of the gas stream. Studies were made primarily with the liquid fuel heptane, although the system can be used with other liquid fuels and with solid fuels. The powder tested was alumina, with 90% by weight of the alumina distribution concentrated in the diameter range of 1.8 - 5.8 mm. At a fixed value of the gas stream velocity, an increase in the oxygen concentration at which extinction occurred. The extinction data can be used to extract overall activation energies and prefactors for the inhibition processes in one-step reaction rate approximations, perhaps ultimately leading to conclusions regarding chemical mechanisms for powder suppression.