Research On Fire And Safety Evacuation Of Immersed Tunnel Based On Flow Field Analysis

With the development of traffic and the progress of tunnel construction technology,long and large undersea highway tunnels begin to emerge in the world,and the subject of tunnel fire also faces greater challenges.How to effectively protect the lives and property of personnel in the fire in the undersea tunnel has become a scientific research issue concerned by scholars studying tunnel fires all over the world.The deep-middle tunnel belongs to a two-way eight-lane immersed-tube highway tunnel,which has the characteristics of large traffic volume and high proportion of trucks.The problems of safe operation and disaster prevention and rescue of the tunnel are quite prominent.In this paper,the author takes the deep-middle tunnel as the research object and uses CFD(Computational Fluid Dynamics(CFD)software as the research method to study the control effect of the tunnel fire prevention system(including jet fan group,independent smoke exhaust system,and spray sprinkler system)on the high temperature and high carbon monoxide smoke flow field generated during the tunnel disaster under different fire conditions,and judges the evacuation results in combination with the personnel safety evacuation software.Through research and analysis,the following main research results are obtained:(1)A total of 16 fire models including different fire source locations,different fire scales,different longitudinal wind speeds and spray systems are studied by taking the tunnel as a model.(2)Under the fire scale of 50 MW and 100 MW,the layout of the smoke exhaust system in the deep middle passage and the design air volume of the fan can meet the evacuation conditions of personnel under various fire scenarios selected in the study,so the smoke control and exhaust system is basically reliable.(3)The results of smoke exhaust system simulating smoke control effect under different fire sources are obviously different.When the fire source is located between the two smoke exhaust crossroads,the highest concentration of carbon smoke in the smoke control area along the driving direction firstly decreases and increases,indicating that when the fire source is located in the middle of the two smoke exhaust crossroads,the concentration of carbon smoke in the smoke control area is relatively low and the smoke exhaust effect is relatively best.(4)The spray system in the tunnel has no obvious effect on the temperature of the smoke flow field and the numerical level of carbon monoxide concentration index when working at the same time with the independent smoke exhaust duct,and has obvious influence on the morphological change of the smoke flow field.The spray system further controls the diffusion range of smoke flow generated by the fire and has a positive effect on the work of the smoke exhaust duct.(5)In the evaluation system of personnel safety evacuation,the traditional empirical formula method is replaced by the evacuation software Pathfinder,which considers more parameters in the evacuation process,and a new and more scientific evacuation system of tunnel fire personnel is formed by combining CFD software to simulate the fire scene.