An Analysis of Pre-Flashover Fire Experiments with Field Modelling Comparisons
Firstly, this report investigates the behaviour of pre-flashover fires conducted in a two-compartment structure. Secondly, it looks at preliminary field modelling results of the pre-flashover fires using the SMARTFIRE program. A two-compartment structure was built so that pre-flashover fire experiments could be conducted. Each room in the compartment measured 2.4 m wide, 3.6 m long, and 2.4 m high. A doorway, with dimensions 2.0 m high and 0.8 m wide separated the rooms. All fires were placed in one room (the fire room) where seven fire experiments were conducted consisting of four differently sized fires. Six of the fires, 55 kW, 110 kW, and 160 kW in size were located in the centre of the fire room. The seventh fire was located in the corner of the fire room and was 110 kW in size. Thermocouple trees were located along the centre-line of the compartment so that vertical temperature profiles could be measured; floor and ceiling thermocouples accompanied the thermocouple trees. In addition, gas sampling points measuring O₂ and CO₂ concentrations were positioned evenly throughout the compartment. Temperature profiles in the fire room revealed constant cool lower layer and hot upper layer temperatures with a sharp temperature gradient between the two layers. Temperatures in the upper layer for the centrally located fires reached 130°C for the 55 kW fire, 200°C for the 110 kW fire, and 250°C for the 160 kW fire. Temperature profiles in the upper layer for the comer fire were not constant with height but showed a temperature gradient, where the temperature reached 335°C near the ceiling. Temperature profiles in the room next to fire room (the adjacent room) showed constant temperature profiles that were close to the ambient temperature in the lower layer. The upper layer temperature profiles displayed temperature gradients that continued up to the ceiling. Temperatures in the upper layer for the centrally located fires in the adjacent room reached 110°C for the 55 kW fire, 160°C for the 110 kW fire, 200°C for the 160 kW fire, and 225°C for the comer fire. Preliminary simulations of the four different fire experiments were conducted using the SMARTFIRE field modelling program. Each fire size simulated twice - one with and one without the six-flux radiation sub-model. A qualitative analysis revealed temperatures in the lower layer of the fire room were under predicted. Temperature gradients were predicted for the upper layer temperature profiles for the centrally located fires, rather than the constant upper layer temperature profiles that were seen experimentally. Overall, simulations predicted closer temperature profiles to the experimental results when the six-flux radiation sub-model was incorporated.