Study On Fire Smoke Flow Characteristics And Optimal Control Strategies In Urban Traffic Link Tunnel

Urban Traffic Link Tunnel which is a new type urban underground traffic system is usually located in the downtown area. Due to the large traffic volume and confined space, once fire occurs in UTLT tunnel, it will cause huge casualties. Statistics showed that smoke is main factor which cause people death and affecting fire fighting. Therefore, it is of great significance to study the characteristics and control strategy of smoke flow in UTLT tunnel fire.With unique characteristics of the dimension and structure, coupled with the effect of longitudinal wind in tunnel, the smoke movement in UTLT tunnel is more particular than that in routine tunnel. The influence of tunnel aspect ratio on ceiling maximum temperature, backlayering and the length of flame are studied, by the methods of theoretical analysis and numerical simulation. The control strategies of longitudinal ventilation and transverse ventilation in UTLT tunnel are preliminary studied by the methods of numerical simulation and small-scale model experiments. The main work and research results of this paper obtained are listed as follows:1) Considering the effect of equivalent diameter and aspect ratio, the function expression of backlayering in UTLT tunnel is obtained by the method of dimensional analysis. Then the backlayering model and confinement velocity model are obtained by FDS numerical simulation. By comparsion the results show that the predicted values of the model are in good agreement with the experimental measurements. This can provide technical support for engineering design of smoke exhaust system in UTLT.2) Considering the effect of fire height and tunnel aspect ratio, the maximum temperature prediction model of UTLT is established with a new calculation method of equivalent diameter. The model can provide guidance for engineering calculation of structure fireproofing in UTLT tunnel ceiling.3) Considering the effect of tunnel aspect ratio, the flame length models in UTLT tunnel with high longitudinal velocity or low longitudinal velocity are established. The models can give guidance for control of safe interval of vehicles in UTLT.4) Smoke extraction volume rate, the pressure of jet fan, arrangement distance of smoke vent and size of smoke vent on the effect of smoke venting are studied by the methods of numerical simulation and small-scale model experiments. The results can give guidance for control strategies of smoke in UTLT.