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Burning Rate Model for Charring Materials.


pdf icon Burning Rate Model for Charring Materials. (4311 K)
Anderson, G. W.

NIST GCR 97-725; 93 p. August 1997.

Sponsor:

National Institute of Standards and Technology, Gaithersburg, MD

Available from:

National Technical Information Service
Order number: PB97-205991

Keywords:

burning rate; char; fire growth; flame spread; pyrolysis; model studies

Abstract:

A one dimensional model has been developed to describe the processes involved in the transient pyrolysis of a semi-infinite charring material subjected to a constant radiant heat flux. Material properties are assumed constant with respect to temperature and time. The model tracks the char layer growth, thermal penetration depth, surface temperature and mass loss rate. A review of the physical phenomena involved in charring pyrolysis is presented and the relevant phenomena included in the model. the integral method is described, and an example for constant surface heat flux is solved. The derivation of the model divides the material into three regions: char layer, vaporization plane, and virgin material and the equations of conservation of mass and energy are applied to each region using the integral approximation with polynomial temperature profiles. The resulting coupled, nonlinear, autonomous system of three different equations and one algebraic equation is suitably nondimensionalized and solved using Mathematics (tm) software. The results generated by the model are compared to existing models and, a method by which effective properties for use in the model might be deduced from experimental data is suggested.