Study On Smoke Flow Characters And Management In Subway Station Fire

Subway is one of the most important public transportation systems in cities. More and more subway systems is built in the world and it is deemed as the symbol of modernization of a city. In China, there are also many subways systems which are being built or in construction in recent years. Subway provides convenient transportation for cities, but also brings many new fire safety problems. Several disastrous subway fires have occurred in recent years, with a great number of victims and substantive loss of properties. Statistics showed that the toxic and hot smoke released due to incomplete combustion were the most fatal factor in subway fires. So, it is very important to study the characteristics and the control strategy of smoke spread in a subway fire.Subway station is a kind of special underground building, it is constitute with a waiting hall floor and a platform floor. Smoke movement in a subway station is more complex than that in a normal compartment. In the thesis, the characteristics and the control strategy of smoke spread are studied by theoretical analysis, small scale experiments, full scale experiments and numerical simulation. Works include:A small scale model of subway station with scale factor of 1/8 was constructed with dimensions of 7.5m×1.5m×0.6m. Full scale experiments were also conducted in three different platforms belonging to exhibition center station and Gangxia station in Shenzhen subway, to validate the efficiency of smoke management system, especially the pressurization effects, in subway station. These experiments provide important data for subway fire research.A model was built for predicting the maximal temperature of ceiling jet in a subway station. The Alpert model is applicable for the situation that the ceiling jet flow is not confined. It was found that in a case of subway fire with a confined ceiling jet; the prediction of Alpert model is some lower. The modification coefficient for the maximal temperature of ceiling jet in case of the ratio of platform's width and height equal to 3 was calculated based on the small scale experiments. The decay of the maximum ceiling jet temperature along with the increase of distance between fire and platform wall was also discovered.A model for predicting the critical velocity of pressurization in subway hall was established by theoretical analysis. It was found that when the heat release rate increases to a certain value, the critical velocity would reach to a maximum value, and does not increase with the increase of the heart release rate any more. The model was further verified by full scale experiments and CFD simulation results. It was proved to be reliable with predictions to be in good agreement with both the measured value in the full scale experiments and predictions by FDS.The characteristics of smoke competition between stairs exist in the two side of subway hall was studied. The former work by Chen Falin's based on the theoretic analysis was modified. Small scale experiments and numerical simulation were conducted to validate the analysis.The smoke exhaust efficiency with different horizontal vent opening heights and velocities was also studied by experiments in a smoke reservoir. The Hinckley model was validated to be reliable in predicting the occurrence of plugholing. FDS simulations was also performed to study the effect of smoke exhaust in the side platform of exhibition center station, the proper vent height and velocity was found according to the experimental data and simulation results. The blind area of smoke exhaust in platform is also found by full scale experiments. An air supply strategy was put forward to solve this problem. The exhaust efficiency under four smoke control schemes were compared by numerical simulation with the best one recommended.