Numerical Simulation Analysis Of Smoke Control And Exhaust System In Shenyang Subway

There have been nearly 200 fire accidents in China since the subway system was put into operation.The fire scene will be a large number of high temperature or toxic smoke enveloped,most of the casualties are not caused by direct fire burns,but by the victims inhaled a large number of toxic smoke,the final poisoning or asphyxiation caused by.It can be said that the reasonable smoke control and exhaust system design in the subway station and the subway tunnel is the guarantee of life safety.In this paper,based on the actual situation of a subway station in shenyang,the physical model of the subway tunnel and the platform area of the station hall is established.After field investigation and literature review,the boundary conditions and fire power of the two models are set respectively,and the mesh independence analysis of the models is carried out,and the appropriate mesh size is selected respectively.Based on the established model,different smoke prevention and exhaust measures are adopted for different situations of subway tunnels and platform areas.The following research is carried out:In the research of smoke prevention and exhaust in tunnel fire,the performance of semi-transverse smoke exhaust system is simulated and analyzed.Firstly,the fire dynamics software Pyrosim was used to set the semi-transverse smoke exhaust conditions with different smoke outlet spacing,smoke emission and smoke outlet sizes.Under the setting of the conditions in this paper,the best working condition is when the smoke outlet spacing is 30 m,and the smoke control effect is optimal.When the smoke discharge quantity is large enough,the greater the smoke discharge quantity is,the better the smoke discharge effect is.On the premise of complying with the velocity regulation of the smoke discharge pipe in gb51298-2018 subway fire design code,the smoke discharge quantity should be increased as much as possible.The area size of the smoke outlet has little influence on the smoke outlet effect.When the smoke outlet is rectangular in shape,the smoke outlet effect is slightly better.Secondly,based on the CO concentration at the respiratory height(1.5m),it is verified that the semi-horizontal smoke exhaust system is reasonable and effective under the condition of reasonable parameter setting,and the smoke temperature in the escape route can be controlled in a lower range,which is conducive to evacuation and fire rescue.Finally,by comparing the smoke extraction efficiency under different conditions,it can be concluded that the smoke extraction efficiency will be reduced when the smoke layer is sucked through the exhaust pipe,and that the smoke extraction efficiency will still increase with the increase of the wind speed at the exhaust pipe when the flow rate at the exhaust pipe brings more benefits than the negative impact caused by the penetration.In this paper,the effect of air curtain in fire accident is mainly verified and evaluated.Firstly,with the mathematical method of orthogonal analysis,four factors and three levels of simulation were used to determine the carbon monoxide reference fraction under different working conditions,and the reference standard for setting the parameters of the smoke curtain was obtained.In the actual design,the jet velocity can be set at 4-5m/s,the jet Angle is set at about 15°,the thickness of air curtain jet is set at about 300 mm,and the moisture content of air curtain jet is set at about 10g/kg.For several parameters affecting the smoke prevention efficiency of the air curtain,the primary and secondary relations are as follows: jet velocity > jet thickness > jet gas moisture content > jet Angle.Since the change of air curtain efflux velocity has the most significant influence on the smoke prevention ability of air curtain efflux,priority should be given to it.Secondly,the research verifies that the influence of air curtain on smoke prevention effect is positive when the air curtain air supply speed continues to increase.However,when the air curtain air supply speed reaches 4m/s,the smoke control effect can achieve a relatively ideal effect and meet the basic requirements,whether the concentration of carbon monoxide or the flow rate of the stairs are consistent with the judgment basis,can effectively cut off the high temperature gas and escape passage.And when the air speed is greater than 4m/s,the smoke blocking effect rises slowly,so it is recommended that the best operating wind speed is 4m/s.Finally,the air curtain in the optimal parameter setting mode is compared with the traditional smoke screen.On the premise of 1000 k W fire source intensity,the air curtain as a flexible partition,compared with the traditional smoke blocking vertical wall anti-smoke mode,in the best mode,the average carbon monoxide concentration of the observation point was reduced by 95.86%,effectively preventing the smoke diffusion,conducive to the evacuation of personnel.