Study On Effects Of Plugholing Under Central Extraction System In Tunnel

Abstract:The central extraction system is the development trend of road tunnel fire exhaust system. And effective use of the exhaust system is the key to engineering design. However, plugholing will reduce the exhaust efficiency of the smoke vent. Plugholing makes exhaust systems cannot be fully utilized. And it could lead to smoke vent congestion, and could easily lead to a negative impact on the evacuation and rescue. For the current rapid development of road tunnel central exhaust system, researches have not been studied deep in the impact of different factors on the smoke layer plugholing. That can’t provide improved guidance in engineering design to prevent the occurrence of plugholing. So there is an urgent need to conduct the research in plugholing occurs in road tunnel under central exhaust system.Firstly, the effect of mechanical exhaust rates, smoke vent distance and smoke vent number is quantitatively discussed by CFD simulation and experimental study. And the typical characteristics of the tunnel when the plugholing occurs is analyzed.By introducing the Froude number, according to smoke temperature and smoke layer depth measured by simulation and experiment, the critical exhaust rate formula and critical Froude number for centralized exhaust smoke tunnel to prevent plughoing are proposed.Moreover, by observing the changes of smoke temperature at different exhaust rates, and introducing the average temperature of the smoke, with the dimensionless of smoke temperature and smoke layer depth, the vertical temperature distribution formula in road tunnel is established. Then, a longitudinal and vertical tunnel network model to calculate the temperature is constructed.In summary, the effects of plugholing under central extraction system in tunnel is studied. And the study expects it can provide reference for our focus on the develop of design specifications of exhaust rate and the select of exhaust vent distance and number.In this dissertation, it counts up to31figures,25tables and62 references.