Multi-layer cable tray fire has special burning characteristics that the cable flame spreads horizontally along cable tray and propagates vertically from bottom layer to upper layer at the same time. With respect of accuracy and speed of calculation, simulation of multi-layer cable tray fire remains a challenge for fire models. In this paper, a method is proposed to simulate multi-layer cable tray fire. By developing a more accurate fire source description, this method can provide accurate simulation for multi-layer cable tray fire rapidly.
In this method, Firstly, the heat release rate of each burning cable tray is evaluated by FLASH-CAT model. Based on the results from FLASH-CAT, a more accurate fire source definition for multiple lay cable tray is developed for zone model. Taking account of each burning cable tray considered as one fire source point, zone model is applied to predict the fire dynamics process. In order to validate this method, four-layer cable tray fire experiments and replicated experiments were carried out in a confined compartment. The histories of mass loss rate of cable tray and temperatures at the middle of compartment were recorded during the cable fire. From the replicated experimental results of total mass loss rate, it is concluded that the four-layer cable tray fire experiment has good repetition in this scenario. Vertical temperature profile shows that the fire circumstance generated by multiple-layer cable tray burning can be divided into upper hot layer and lower cool layer, which conforms to the basic assumption of zone model. As a consequence, the zone model can be applied to simulating multiple-layer cable tray fire.
By comparing the experimental total heat release rate with predictions, it is found that characteristics of multiple-layer cable tray fire are well captured. On account of good prediction on overall heat release rate for multi-layer cable tray fire, predicted heat release rate for each burning cable layer by FLASH-CAT model is believed to be reliable. Then, each burning cable layer is set as one fire source and the heat release rate of each burning cable layer is input into zone model, respectively. The comparisons between simulations and experimental data show that the predicted upper layer temperature and lower layer temperature agree well with experimental data. As a result, it can be concluded that this method provides reliable prediction for multiple-layer cable tray fire rapidly.
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