Pressure Equations in Zone-Fire Modeling.
Pressure Equations in Zone-Fire Modeling.
(1285 K)
Rehm, R. G.; Forney, G. P.
Fire Science and Technology, Vol. 14, No. 1/2, 61-73,
1994.
Keywords:
zone models; fire models; pressure; equations;
exothermic reactions
Abstract:
The nonadiabatic nature of low-speed combustion and
fire, in which strongly exothermic reactions produce
large temperature variations but only mild pressure
variations, can cause difficulty when integrating zone
models of enclosure fires. Examples of simple zone fire
models are examined to illustrate the analytical nature
of the problems encountered. These difficulties arise
in the solution of the equations for the pressure in
general enclosures because the pressure equilibrates
much more rapidly than other dynamical variables.
Singular perturbation methods and phase plane analyses,
together with numerical integration of the
nondimensionalized equations, are employed to study the
stiff nature of the equations. We conclude that many of
the difficulties associated with numerical integration
of zone fire models may be circumvented by appropriate
analysis of the zone fire model equations.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899