Study On Smoke Movement Of Subway Fire In Long Tunnel

With the development of the society and the acceleration of urban construction,more and more cities are building subways to meet the traffic needs.However,the increase in the number of subway lines and the increase in the complexity of crossing also bring more hazards.Based on the analysis of subway tunnel fire research at domestic and foreign,this paper uses numerical simulation to investigate the influence of moving fire on temperature distribution and smoke spread in the tunnel,which lays the foundation for the prevention and rescue of subway tunnel fires and personnel rescue.Firstly,the factors affecting of the heat release rate of the same source is studied.The variation trend of the heat release rate and heat loss of the source are analyzed by changing the wind speed,effective height and longitudinal position of the source.The results show that longitudinal ventilation can increase the heat release rate.However,the decrease of effective height will reduce the combustion efficiency of the fire,which leads to the decrease of the heat release rate.For the longitudinal position of the fire source,the change of heat release rate is related to ventilation and the blocking of the vehicle body,and the fire is most dangerous when it is located at the top of the rear.Secondly,a tunnel train motion model was established,and the critical speed was determined by comparing the temperature and smoke.By simulating the fire of moving train at critical speed,it was found that the movement of fire caused the plume to shift from the impact area of the ceiling,and the smoke accumulated.However,due to the lack of thermal buoyancy,the spread of the rear smoke cannot maintain the layered structure,and the spread distance of the smoke has not continued to increase.Finally,the coupling of ventilation and train motion is studied.It was found that the reverse ventilation can reduce the temperature of the flue gas under the tunnel roof,but the spread of the flue gas is greatly increased.The same direction ventilation can control the spread of flue gas in the direction of the rear of the vehicle,but it has a greater impact on the locomotive.