Accession Number : ADA327241

Title :   Extinction Studies of Polyfluoropropanes and Halons in Methane/Air and Propane/Air Counterflow Diffusion Flames.

Descriptive Note : Interim rept. Oct 96-Mar 97,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s) : Williams, Bradley A. ; Fleming, James W. ; Sheinson, Ronald S.

PDF Url : ADA327241

Report Date : 27 JUN 1997

Pagination or Media Count : 18

Abstract : Several fluoropropanes have been tested for fire suppression in methane/air and propane/air diffusion flames. The agents were added to the air stream, and tne variation in the air stream extinction flow rate as a function of agent concentration was recorded. Significant isomeric differences were observed in suppression effectiveness of the penta-, hexa-, and heptafluoropropanes. The agents' effectiveness depended principally on the number of CF3 groups in the molecule. The most efficient fluoropropane agents were perfluoropropane (FC-218), 1,1,1 ,2,3,3,3-heptafluoropropane (HFC-227ea), and 1,1,1 ,3,3,3-hexafluoropropane (HFC-236fa), all with two CF3 groups. The fluorine/hydrogen ratio in the agent was found to have only a minor effect on suppression, with a higher fluorine content producing slightly better inhibition at low agent concentrations. The relative rankings of the agents were essentially identical for methane and propane fuels. Cup burner tests of HFC-227 and HFC-236 isomers with n-heptane and methanol fuels find the same isomeric differences. These observations indicate that hydrofluorocarbons possess a significant chemical suppression of combustion, and that CF3 groups are critical to this suppression. In the propane/air flames, four halons were also tested: CF3Br, CF3I, CF2ClBr, and CHF2Br. The relative effectiveness of these agents also demonstrates a significant chemical effect of CF3 groups.

Descriptors :   *EXTINCTION, *POLYMERS, *AIR FLOW, *FLUORINE, *DIFFUSION, *FLAMES, *METHANE, *FIRE SUPPRESSION, *HALOGENATED HYDROCARBONS, *PROPANE, CHEMICAL COMPOSITION, ISOMERS, COMBUSTION, FUELS, METHANOLS, LOW LEVEL, INHIBITION, CONCENTRATION(CHEMISTRY).

Subject Categories : Organic Chemistry
      Polymer Chemistry
      Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE