Characteristics Of Moving Fire In Long And Confined Subway Tunnels

Subway tunnels play an important role in the urban rail transit,which belong to the confined space.Although the probability a subway train fire in the tunnel is small,once it occurs,it will bring unpredictable losses to urban rail transit.This paper is aimed at the simulations and experimental research of the characteristics of the moving fire in the subway tunnel.Furthermore,it also include the study of the characteristics of the piston wind which affects the smoke movement.Firstly,the experiment study and numerical simulation of the moving tunnel fire are carried out.The similarity theory of the model experiment is used to determine the number of criteria to be followed in the design of the experimental system,and the experimental system of the single-movement fire scale reduction based on absolute motion is designed.The heat release rate of the fire source of the shrinkage experiment system is determined by pre-experimental study.Then,a new method of meshing is proposed,which is suitable for the coupling calculation in CFD numerical calculation.And the accuracy of the calculations for the numerical model in the velocity field and the temperature field is verified by the test data of typical experimental conditions.Secondly,the model of the piston effect and temperature distribution of tunnel moving fire are established.The Bernoulli method is used to model the subway piston effect which affects the flue gas spread.The accuracy of the theoretical model is verified by using the test data and the experimental results by predecessors.The theoretical model of the temperature distribution of the moving tunnel fire is established by using the relative coordinate system and the accuracy of the theoretical prediction model is verified by the experimental data.By studying the effects of the moving speed,the deceleration speed and the fire power,an effective means to control the countercurrent of the fire smoke is put forward.Thirdly,the theoretical model of critical wind pressure models is established.And,the effects of different train speeds,braking deceleration,fire source power on the countercurrent distances and critical wind pressure are studied.The maximum temperature rise of the case of 2m/s is 75.50% lower than that of 1m/s.Finally,the wind coupling and the critical wind pressure model of the multi-motion body are established for the two trains traveling in the same direction.In this paper,a typical engineering example is used to study the comparison of different smoke extraction schemes.This paper is proposed with a vertical smoke exhausting strategy for the alternative ventilated wind shafts which are suitable for the fissure of the moving fire in the long subway tunnel.