AN EXPERIMENTAL AND MODELING STUDY OF FIRES IN VENTILATED DUCTS .2. PMMA AND STRATIFICATION

A theoretical and experimental treatment of fire processes in horizont al, ventilated passages, containing an axial distribution of fuel, is presented. Experiments for radially well-mixed flows are performed whe re gas temperature histories and fire-shaped solid fuel mass axial dis tributions are acquired from polymethyl methacrylate (PMMA)-fueled fir es. The theory developed in part I is able to quantitatively model all the experimental results for PMMA fires. In particular, the solid fue l profiles (axial distributions) are modeled from gas-phase informatio n alone. To assess the concept of an ignition temperature as a control ling mechanism for growth a brief fire growth analysis is also perform ed. A simple approach to study fires in stratified flow conditions is also presented. In conjunction with small-scale experiments on liquid- fueled fires it is shown that a modified one-dimensional model, requir ing minimal computational effort, may be used to describe fire-front h istories and the temperature profile of the fire plume. Both nonstrati fied and severely stratified fires display a direct dependence of the steady fire propagation speed with ventilation rate and inverse depend ence with initial fuel mass loading. A general model requires a knowle dge of the degree of stratification and mixing, in advance of experime ntation. A new correlation for stratification using fuel/duct properti es and air velocity is proposed as a means of predicting flow regimes.