Study On Smoke Temperature Distribution In Point Exhaust System Tunnel Fire

In recent years,our modernization process is speeding up,the highway tunnel construction has entered the high speed development period.Due to the lengthening of highway tunnels in China,the increasing transportation of dangerous goods and the increasing traffic density,tunnel fire accidents frequently occur and cause serious consequences,which brings serious threats to people’s life and property safety.Therefore,the early detection and prevention of tunnel fire becomes an urgent problem to be paid attention to and solved.It is of great practical significance to study the smoke temperature distribution in tunnel fire for fire detection and early prevention,and to provide guidance for the installation of fire alarm and the placement of fire extinguishing facilities.150 sets of fire experiments were carried out in a 1:10 reduced tunnel by changing the size of the pool,the distance between fire source and smoke vent,and the amount of concentrated smoke exhaust.The development process and shape of the fire plume during the pool fire with different sizes were studied.The effects of the size of the pool,the distance between fire source and smoke vent,and the amount of concentrated smoke exhaust on the heat release rate of the fire source were analyzed.The results show that the plume of pool fire presents different states in four combustion stages: initial combustion stage,transition stage,stable combustion stage and gradual extinction stage.In the stable combustion stage,the top of the fire plume of 10cm×10cm pool contacts the ceiling intermittently,while the burning plume of the larger size pool continuously contacts the ceiling.The quality loss of the pool fire is mainly affected by the size of the pool,but does not change significantly with the smoke emission and the location of the fire source.The heat release rate of fire source increases with the size of pool.Combined with the tunnel fire experiments,the effects of fire power,fire location and smoke emission on the tunnel longitudinal temperature distribution are qualitatively analyzed.The results show that the longitudinal smoke temperature increases with the increase of fire power.The farther the fire source is from the smoke vent,the lower the temperature when the smoke spreads to the smoke vent;The maximum temperature of ceiling smoke is always above the fire source.The maximum temperature of ceiling smoke decreases with the increase of exhaust volume.The amount of exhaust smoke has a great influence on the temperature of smoke within 1m from the fire source.Through dimensional analysis,three parameters of fire source power,fire source position and smoke emission were dimensionless,and a prediction model of the maximum temperature rise of smoke in the fire ceiling of point smoke exhaust tunnel was established.The results show that the maximum temperature rise of smoke is proportional to the 0.034 power of the non-dimensional fire source position,and increases with the increase of the power of fire source.Finally,the applicability of the prediction model in full-scale tunnel fire was verified by numerical simulation of full-scale tunnel.The results show that the mathematical model of ceiling smoke maximum temperature rise can effectively predict the maximum temperature of smoke in full-scale tunnel fire with the key smoke exhaust mode.Figure [48] Table [14] Reference [88]...