Numerical Simulation Of Fire-induced Smoke Movement In Compartment

In modern times,High-speed trains have become one of the most important means of transpor.It has the advantages of high speed,large capacity,good comfort,large conveying capacity and so on.In recent years,train fire accidents take on frequently which resulted in heavy casualties and property losses.The statistical results show that more than 85%of the deaths in the fire are caused by smoke.Therefore,it is of great significance to study the smoke control strategies for compartment fire.In order to study the law of fire-induced smoke flow in train compartment under different conditions,one compartment's internal space of the high-speed train CRH2A was set as the research object.Based on computational fluid dynamics and the science of combustion,typical fire scenarios were simulated and calculated by using Pyrosim simulation software.7 working conditions were set up according to fire source power,carriage door open status and fire locations.The results show that:(1)HRR(heat release rate),smoke temperature and CO concentration rises with the increase of fire power;(2)Smoke distribution is greatly influenced by carriage door open status,it's well-ventilated combustion when the doors are open,either HRR or Fire HRR is relatively higher;the smoke velocity increases gradually.However,it's under-ventilated combustion when the doors are closed and fire is self-extinguishing due to insufficient oxygen during the combustion process.Fire source power has little effect on HRR and Fire HRR,and the smoke velocity firstly increases then decreases;(3)When the fire source is located in the central seat of compartment,smoke concentration and smoke temperature are symmetrically distributed around the fire source,and they reduce with the distance from fire source.When the fire source is located in one end of the carriage(closed to the door),smoke concentration decreases with the distance from fire source,and the maximum value is near the fire but not over it.Smoke temperature changes in the same way;(4)The pressure distribution in the compartment increases from bottom to top.Pressure in the upper space is positive,and the bottom space is negative.8 working conditions were set up according to three ways of smoke control and extraction:without smoke exhaust system,mechanical smoke exhaust system and the coupled system.The results show that:(1)Comparing with V(mechanical exhaust rate)is 0m~3/s,when V is 0.87 and 2m~3/s,final smoke average temperature decreases 46.4%and 58.2%,respectively;(2)When V is 0.25,0.87 and 2m~3/s,the time of visibility to critical value is respectively prolonged 30%,54%and 98%compared to V is 0m~3/s;(3)Under the conditions of this paper,when V is 2m~3/s,the effect of air curtain outlet velocity on smoke temperature and visibility is not obvious.But,the effectiveness of smoke-preventing will be better with the increase of air curtain outlet velocity;(4)To some extent,the effect of mechanical smoke exhaust on reducing smoke temperature and concentration is more obvious than that of air curtain system.Air curtain can help to impede and delay the spreading of smoke to adjacent carriages,but the visibility inside will decrease.The effectiveness of smoke-preventing with air curtain does not interfere with the mechanical exhaust system.Therefore,it can be taken as a selection of smoke control technology.