Research On Plugholing Of The Point Smoke Extraction In Highway Tunnel

In recent years,highway tunnel has made great progress in terms of quantity and length,and the tunnel fire accidents has also increased.The smoke with high temperature produced by tunnel fire is the main factor that threaten the safety of trapped people.In the smoke exhausting mode of the tunnel,the point smoke extraction mode can control the smoke in a small range,and can quickly discharge the tunnel,which has a better effect of exhaust smoke.But in the process of point smoke extraction,the plugholing may occur at the smoke vents,which reduces the efficiency of exhaust smoke and extremely unfavorable to the evacuation of trapped people and the development of rescue work.This paper will mainly study the relevant factors that affect the phenomenon of plugholing.This article first analyzes and summarizes the characteristics,hazards,and the law of occurrence and development of tunnel fires,summarizes the research status of tunnel fires both at home and abroad,and then uses the fire dynamics software PYROSIM to conduct a dimensional simulation test on the point smoke extraction modes of tunnel fires.The full text mainly carries on the research work in the following four aspects.(1)Study the influence of the axial fan exhaust smoke velocity at the two ends of the tunnel on the smoke vents plugholing phenomenon.(2)Study the influence of the number of smoke vent openings on the smoke exhaust plugholing phenomenon.(3)Study the influence of the distance between the smoke vent on the smoke exhaust plugholing phenomenon.(4)Study the influence of the size of the smoke vent on the phenomenon of plugholing.The data obtained from numerical simulation were analyzed and studied from the thickness of the smoke layer,the CO gas content,the total exhaust smoke volume,and the temperature,to find out the influence on the smoke vents plugholing phenomenon and to sum up the relevant rules.The results show that the smoke vents near the two ends of the axial flow exhausting fan(the farthest point away from fire)first undergoes the phenomenon of plugholing with the increase of the exhaust gas rate;When the number of smoke vents that are opened is small,the corresponding rate of smoke exhaustion during the phenomenon of plugholing is greater.When the distance between the smoke vents is small,the phenomenon of plugholing is less likely to occur.When the phenomenon of plugholing occurs,the exhaust rate is relatively large.When the size of the smoke vent is small,the phenomenon of plugholing does not occur easily;The two exhaust outlets that are furthest from the axial fans at the two ends of the tunnel(closest to the ignition point)have no phenomenon of plugholing within the range of the exhaust rate set by numerical simulation.This paper studies the plugholing at the smoke vent in the point smoke extraction mode of highway tunnel fires,enriches the relevant researches on the point smoke extraction modes of highway tunnels,and provides the relevant reference for how to prevent plugholing in the design of the smoke exhaust port.