Abstract
The requirements for the occurrence of travelling fires and their distinction from previously recognized stages of fire development are not well understood. Here we present a CFD method that couples a fuel-area correction to a single-step wood pyrolysis model. The model was validated using SP medium-scale tunnel, demonstrating 19% under-prediction in peak HRR, and BST/FRS large-scale compartment where the predicted temperatures were within ±6% of the measurements. Detailed simulations of compartment geometries identified three modes of fire propagation: (1) With high ceiling heights, the ignition was followed by a fuel-controlled spread/travelling at speeds <1 cm/s (2) With lower ceiling heights, we observed a rapid (1–9 cm/s) spread towards the opening, driven by the smoke layer radiation and leading to a ventilation -controlled fire. (3) Finally, fire travelled back to the compartment interior at speed 0.1–0.9 cm/s, driven by large flames and controlled by the fuel-burnout.The analytical travelling fire model is designed to describe the first mode, but could also be used for modelling the back-travelling stage. Comparison between the CFD simulation and the analytical model indicates that further development of the analytical model is needed to account for the compartment's heating history and tunnel -like geometries.
Highlights
The issue of fire spread modelling and its implications on the response of structures is an active research topic that has recently gained immense interest
Even though the simulations specify the same mass as reported in the experiments, the heat release rates (HRR) behaviour implies that oxidation of char plays an important role during the extinction phase
Combinations of the ignition temperature and single-step kinetics -based pyrolysis models were used in the validation simulations
Summary
The issue of fire spread modelling and its implications on the response of structures is an active research topic that has recently gained immense interest. After multiple fire accidents (the Interstate bank fire in Los Angeles, One Meridian Plaza fire in Philadelphia, World trade centre fires, Windsor tower in Madrid and Faculty of Architecture at TU Delft) where the fires had been observed to move along the floor and vertically across different floors, the prescriptive approach of the Eurocodes [1] was found to be insufficient to ensure fire safety in large complex structures These fire scenarios are being classified as travelling fires based on the travelling fire model that was proposed by Stern-Gottfried and Rein in 2012 [2]. In case of local fuel burnout, ignition and extinction fronts are formed, and a semi-steady state propagation of a fire line of constant width can be observed Other factors, such as ventilation, may limit the power even when the area increases
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