Research On Smoke Extraction Model Of Subway Stations Based On Fire Simulation And Personnel Evacuation

With the accelerated urbanization and further expansion of urban scale in China,the subway has the advantages of fast,punctual,and large capacity,so it gradually becomes an important part of the urban public transportation system.However,subway stations are mostly underground,with long and narrow structures and dense personnel,which can easily cause a large number of casualties and property damage in case of fire.In subway fires,fire smoke is the main factor leading to casualties,and an effective smoke extraction mode can remove smoke and reduce human injuries.Therefore,it is important to study the smoke exhaust mode of subway station fires to ensure the life safety of people in the station.In this paper,we apply the numerical simulation method to establish the fire calculation model and personnel evacuation calculation model of a typical double-decker island subway station,and study the smoke spread,personnel evacuation,and fire safety degree of subway fire under different smoke evacuation modes,and optimize the smoke vent design of subway smoke evacuation mode.First,based on fire dynamics,this paper simulates and calculates three fire scenarios and five smoke evacuation modes for a total of 15 working conditions,analyzes the distribution of parameters such as subway fire temperature,visibility,CO concentration,and smoke velocity,and applies the fire safety risk assessment method to calculate the total safety index for each working condition,and compares the effects of various smoke evacuation modes.The results show that mechanical smoke extraction can improve the evacuation conditions and increase the total safety index of the subway station;the increase of firepower and the restricted space around the fire source will lead to an increase in fire risk;mechanical smoke extraction can reduce the temperature and CO concentration in the subway station and improve the visibility conditions compared with natural smoke extraction,which can effectively improve the total safety index of the subway station;lateral smoke extraction can improve the total safety index compared with longitudinal smoke extraction,and the evacuation conditions of the station can be improved.The lateral smoke exhaust improves the overall safety index and improves the evacuation conditions of people in the station;the station lobby air supply can effectively inhibit the spread of smoke in the station lobby;the lateral smoke exhaust mode coupled with the station lobby air supply has the best smoke control effect.Secondly,based on evacuation kinetics theory,this paper investigates the evacuation process under different smoke exhaust modes,and couples the influence of fire products to make the evacuation simulation closer to reality.The results show that: the safest fire scenario with the fire source in the center of the platform and the firepower of 2 MW can be safely evacuated under all smoke exhaust modes;the most dangerous fire scenario is a 5 MW fire with the fire source on the left side of the platform,and a large number of people are seriously injured in the fire scene;the most dangerous fire scenario can achieve better evacuation by applying the smoke exhaust mode of lateral smoke exhaust coupled with an air supply in the station hall.In the most dangerous fire scenario,the lateral smoke exhaust coupled with the station hall air supply mode can achieve a better evacuation effect,and the people can be safely evacuated within the specified time.Finally,this paper applies the numerical simulation method to optimize the smoke venting mode,calculates and analyzes five types of smoke vent opening quantity,three types of smoke vent height,20 types of smoke vent baffle design,and analyzes the CO concentration distribution,smoke layer height,temperature distribution and personnel evacuation in the station for these working conditions.The results show that: the appropriate reduction of the number of smoke vent openings can improve the smoke exhaust efficiency,but too few smoke vent openings will lead to a reduction in the smoke exhaust coverage area,and the smoke exhaust effect is better when the number of smoke vent openings is 20;the increase in the height of the smoke vent is conducive to the improvement of smoke exhaust efficiency,which can reduce the area of the high temperature area of the station and reduce the concentration of CO,and the smoke exhaust effect is better when the height of the smoke vent is 3.7 m,which is conducive to the improvement of smoke exhaust efficiency;the smoke venting flow field can be improved by adding smoke vent baffle at the smoke vent,but the angle and width of the smoke vent baffle need to be chosen reasonably;the smoke venting effect is better when the angle of the smoke vent baffle is 30° and the width of the smoke vent baffle is 0.6 m;compared with the lateral smoke evacuation mode before optimization,the optimized smoke evacuation mode improves the overall safety index by 9.9% and reduces the time required for evacuation by 14 s.The overall safety of the station platform has been improved.The optimized smoke extraction mode can improve the total safety index and reduce the evacuation time of the subway station.