Predicting flammability limits through thermal theory and density theory of flame propagation

Abstract

SUMMARY Flammability limits are important safety parameters of each flammable material. Thermal theory of flame propagation suggests existence of a threshold temperature above which a flame propagates. Density theory of flame propagation suggests existence of a threshold density factor above which a flame propagates; density factor is defined as the ratio of before ignition to after ignition density. Based on a general version of thermal theory of flame propagation, constancy of values of adiabatic flame temperature at each flammability limit can be used to predict flammability limits. Similarly, based on a general version of the density theory of flame propagation, constancy of values of density factor at each flammability limit can be used to predict flammability limits. This work reports and compares predictions of general versions of both thermal theory and density theory of flame propagation for lower flammability limits and for upper flammability limits. This work shows that thermal theory and density theory both perform well at predicting the lower flammability limit while density theory performs far better than thermal theory at predicting the upper explosive limit.