Modelling the generation of toxic combustion products and its transport in enclosure fires

Mahalingam, Arun (2007) Modelling the generation of toxic combustion products and its transport in enclosure fires. PhD thesis, University of Greenwich.

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Abstract

Most common building materials are polymer based. Thus toxic products evolving from burning polymers is the single most important factor in fire fatalities. Fire hazard calculations require modelling of heat generation, toxic combustion products generation and its transport in realistic building scenarios involving common building material. However, the thermal decomposition, combustion behaviour and chemical kinetics for common polymers like wood, plastics, rubber and textiles are extremely complex.

In the present study, a methodology (STEM-LER: the Scalar Transport Equation based Model using the Local Equivalence Ratio concept) based on solving separate transport equations for the species and using the yield correlations obtained from bench-scale experiments to model the source terms is proposed to predict the products generation and its transport during enclosure fires. Modelling of complex solid phase degradation and chemical kinetics of polymers is bypassed by measuring the product yields as a function of equivalence ratio by burning the samples in a bench-scale combustion apparatus called Purser furnace.

Since the accuracy of prediction depends upon the quality of the yield data obtained from the Purser furnace, attempts were also made to numerically investigate this bench-scale toxicity test method in order to understand its modus operandi.

Finally, a preliminary assessment on the effect of cable fires on building evacuation for the simulated fire scenarios was carried out using a sophisticated evacuation model.

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