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Ionic Effects in Initiation of Ignition Surface Mediated Superbase Reactivity.


pdf icon Ionic Effects in Initiation of Ignition Surface Mediated Superbase Reactivity. (1174 K)
Bannister, W. W.; Chen, C. C.; Euaphantasate, N.; Morales, A.; Tapscott, R. E.; Vitali, J. A.

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, 467-479 pp, 2000.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

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/

Keywords:

halon alternatives; ignition; oxidation; vapor phases; ignition temperature; natural gas; hot surfaces; halons

Abstract:

There are two generally accepted indices regarding fuel flammability. The more commonly used index is the flash point of the fuel (either closed or open cup), which is the minimum temperature for a liquid fuel to sustain sufficient levels of vapor concentration in the air immediately over the surface to produce ignition when an open flame is passed directly over the surface. There is therefore the requirement for a preexisting flame. Autoignition temperature is the minimum temperature of a fuel "required to cause self-sustained combustion, independently of the heating or heated element." (Since the term "Autoignition Temperature" does not directly evoke the concept of surface effects, the synonymous term "hot surface ignition temperature" [HSIT], or more simply ignition temperature, will instead be used throughout this paper, which will delve principally on effects of surfaces on autoignition.) In this determination, there is no open flame involved in the ignition. Ignition temperatures are typically determined by applying minute portions of the fuel onto a hot surface and waiting for up to 10 minutes until ignition is observed (either visually or with thermoelectric sensors). If there is no ignition, the process is repeated with increasing temperatures, until ignition is finally achieved. There are a number of flame processes, including hot-flame ignition (as indexed by autoignition temperatures (AIT), accompanied by a "rapid, self-sustaining...readily visible yellow or blue flame"); cool-flame ignition ("relatively slow, self-sustaining barely luminous...cool flames visible only in a darkened area"), indexed by cool-flame reaction threshold (CFT, "the lowest temperature at which cool-flame ignitions are observed"); and pre-flame reactions, indexed by preflame reaction threshold (RTT, the lowest temperature at which exothermic gas-phase reactions are observed").