Citation

Thomas PH. Fire Safety J. 1980; 3(1): 67-76.

Copyright

(Copyright © 1980, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

A simplified form of energy balance for a quasi steady compartment fire is presented. It allows for mass transfer in a partially vitiated but uniform atmosphere and for a thermal feedback approximately representing the radiation from hot gases and walls.According to the magnitudes of two dimensionless parameters, one, characteristic of the ratio of heat generation to wall loss, and the other, characteristic of the non-linear feedback, one obtains eight types of relation between burning rate and ventilation rate. Several of these regimes exhibit a thermal instability that has already been taken to represent one kind of 'flashover'. It arises from an increase in fire area or a reduction in the ventilation. One regime, however, exhibits a second instability that arises from an increase in ventilation. The first is thus consequent, primarily, on reducing cooling, the second on increasing the oxygen concentration, which, in turn, leads to a fall. Both these falls in oxygen concentration lead to ventilation-controlled burning.Newer materials include some which may be more prone to these instabilities than are traditional materials.