NIST Time|NIST Home|About NIST|Contact NIST

HomeAll Years:AuthorKeywordTitle2005-2010:AuthorKeywordTitle

Suppression Effectiveness Screening for Impulsively Discharged Agents.


pdf icon Suppression Effectiveness Screening for Impulsively Discharged Agents. (378 K)
Grosshandler, W. L.; Hamins, A.; Charagundla, S. R.; Presser, C.

Halon Options Technical Working Conference. Proceedings. HOTWC 2000. Sponsored by: University of New Mexico, Fire Suppression Systems Assoc., Fire and Safety Group, Great Lakes Chemical Corp., Halon Alternative Research Corp., Hughes Associates, Inc., Kidde Fenwal, Inc., Kidde International, Modular Protection, Inc., Next Generation Fire Suppression Technology Program, Sandia National Laboratories, Summit Environmental Corp., Inc. and 3M Specialty Materials. May 2-4, 2000, Albuquerque, NM, 15-25 pp, 2000.

Available from:

For more information contact: Center for Global Environmental Technologies, New Mexico Engineering Research Institute, University of New Mexico, 901 University Blvd., SE, Albuquerque, NM 87106-4339 USA.
Telephone: 505-272-7250,
Fax: 505-272-7203. WEB: http://nmeri.unm.edu/cget/confinfo.htm

Keywords:

halon alternatives; fire suppression; aircraft safety; solid propellants; test methods; experiments; injection; halon 1301; halons

Abstract:

Agent suppression effectiveness is typically measured by experiments in quasi-laminar diffusion flames established in a cup burner or counter-flow burner. Those experiments are conducted by increasing the agent flow slowly until a critical mole fraction is achieved in the oxidizer and flame extinction is observed. In practice, however, agents designed to replace CF3Br are discharged rapidly, not quasi-statically. Solid propellant gas generators (SPGG), for example, typically discharge in 10 ms to 500 ms. A robust and repeatable means to evaluate the effectiveness of different formulations and burning rates is required, something that is impossible with conventional screening devices. Hirst, Dyer, and coworkers developed a wind tunnel to explore the impact of step height, air flow, pressure, and agent mass requirements on the suppression of a pool fire and concluded that liquid pool fires established behind an obstacle are highly challenging to extinguish. Hamins et al. developed a phenomenological model to characterize the stability of baffle stabilized fires. Takahashi et al. examined the character of methane/air flames for varying air velocity and baffle step height, and measured the amount of Halon 1301 required to suppress the flames as a function of the flow parameters and injection interval. The transient-agent recirculating-pool-fire (TARPF) suppression facility was designed to screen the performance of agents that are applied suddenly and for a short duration. The TARPF facility, originally described at the 1999 Halon Options Technical Working Conference, consists of a horizontal wind tunnel designed to simulate challenging fire situations and to control precisely the air flow, amount of agent, discharge rate, and discharge duration. Air is metered through a sonic orifice to overcome the unintended disruption that occurred in some previous studies during the agent discharge period. The influence of common geometric complexities (baffles, a backward-facing step, and a cavity) on flow field dynamics and flame stability and a relationship between the mass of agent necessary for suppression and the agent injection duration are described in a paper by Grosshandler et al. Direct numerical simulation of flame suppression is used in that paper to help explain the observations. The capability to test solid-propellant gas generators has been added to the TARPF. For the first time, both compressed and solid-propellant generated gases can be compared side by side. It is now possible to discriminate among formulations, particle loadings, and burning rates for various SPGG designs. The SPGG injection system and measurement method are described in this paper, and the results from experiments with a commercial air-bag gas generator are presented.