The generation rate and distribution of products of combustion in two-layer fire environments: a model and applications

Abstract

A model is developed for predicting the generation rates of oxygen, fuel, and other products of combustion in rooms containing fires and time-dependent fire environments. The model is called the Generalized Global Equivalence Ratio Model (GGERM). It extends the steady state global equivalence ratio model established previously from data of several steady state experimental studies. After describing the GGERM, a concise algorithm is outlined for implementing it in two-layer zone-type compartment fire models. With the algorithm in place, such models could be used to simulate the distribution of combustion products in single or multi-room fire environments under conditions of arbitrary ventilation. In example applications, the GGERM is used to simulate the time-dependent environment, including that of steady state, in some of the above-mentioned experimental studies. For arbitrary experimental conditions and for both complete stoichiometric combustion and ‘real’ combustion of methane (CH 4), solutions for concentrations of products of combustion are obtained and presented. For the case of complete stoichiometric combustion, the solutions are used to predict the time-to-extinguishment of a burning CH 4 fuel source embedded in an initially ambient-atmosphere upper layer. In another application, the GGERM is used to simulate the combustion of hexane (C 8H 14) in an enclosure fire scenario where data has been reported in the literature. Predicted and measured concentrations of fuel and products are found to compare favorably.