- Author
- Mitler, H. E.
- Title
- Predicting the Spread Rates of Fires on Vertical Surfaces.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Book or Conf
- Combustion Institute, Symposium (International) on Combustion, 23rd. July 22-27, 1990, Combustion Institute, Pittsburgh, PA, Orleans, France, 1715-1721 p., 1991
- Keywords
- combustion | flame spread rate | slabs (members) | algorithms | heat flux | pryolysis rate | equations | polymethyl methacrylate
- Abstract
- A model is developed for the upward spread rate of the pyrolysis front of a burning vertical slab. It is ignited with a flame from a line burner of user-specified strength. It can also be exposed to arbitrary, time-varying impinging external fluxes. It is assumed that the slab material has uniform, isotropic properties and that there is no lateral diffusion of heat withing the slab. This model has been implemented as a computer program. The program has two options for the mass-loss rate. The first uses an algebraic submodel for the steady-state pyrolysis of simple, non-melting and non-charring materials. The second is based on Cone Calorimeter data: the mass-loss rate data found via the Cone at a given irradiance level is transformed into what the rate would be at those found during the actual experiment. The latter approach automatically includes the effects of charring, of transient heating, etc., to a first approximation. Expressions for the heating flux from the flame to the wall are found for all cases of interest. Runs were made assuming 2.5, 5, and 10 kW/m igniting burners and with a square-root dependence on [equation] for the flame height, as well as with the usual 2/3 power dependence. The results of each run were compared with the results of upward spread experiments on PMMA carried out in 1975 by Orloff, et al. The results, using either mass-loss rate option, were in excellent agreement with experiment when the square-root dependence was used.