Experimental study on the smoke temperature distribution of cable tray fires of utility tunnel under different entrainment restriction conditions
In order to enhance the prevention and control of cable tray fires in utility tunnels,this study conducted a full-scale cable tray fire test and systematically investigated the influence of the number of cable layers and the effects of entrainment restriction on the distribution of smoke temperature in cable tray fires.A series of thermocouples were placed both vertically near the cable tray fires and horizontally beneath the ceiling to measure the vertical and horizontal temperature distribution of the utility tunnel.Based on the vertical temperature distribution in utility tunnels,the vertical temperature stratification patterns caused by the settling of smoke from cable tray fires in utility tunnels were revealed.Results show that,when cable tray fire happens,the utility tunnel can be divided into three parts from top to bottom:the top jet layer,the middle hot smoke transition layer,and the bottom cold air layer.By analyzing the transverse smoke temperature distribution beneath the ceiling at different ports of the utility tunnel,it is found that the rate of temperature decay at the semi-closed end is faster than that at the fully closed end.Additionally,a dimensionless longitudinal temperature distribution model,considering the heat release rate and the effective source-ceiling height,was established for the fully enclosed end roof.Finally,based on the relationship between the air entrainment restriction and the maximum temperature rise beneath the ceiling,it is found that the cable tray fire is significantly influenced by the thermal feedback from the side wall and end wall when the overall ignition source power is higher.A prediction model was developed for the maximum temperature rise of the roof in cable tray fires,considering the restrictions on air entrainment from the sidewall.By comparing the model's predictions with the experimental results,it is found that the model error was less than 16％.Findings of this study provide guidance for the fire prevention of cable tray fires in utility tunnel.
safety engineeringutility tunnelcable tray firesmoke temperature distributionentrainment restriction
NETL
NSTL
万方数据
维普
