| Lateral centralized smoke exhaust system is a new type of smoke exhaust mode which integrates the advantages of longitudinal and lateral smoke exhaust systems.With its unique advantages,such as hindering the longitudinal transition and spread of smoke,maintaining the stability of smoke layer and reducing project cost,it is gradually applied to the construction of underwater tunnels in China.However,at the present stage,the research on the lateral centralized exhaust system is relatively scarce.Under the coupling effect of the suction force,the resistance along the way and the lateral negative pressure generated by the lateral centralized exhaust system,the flue gas flow will be more complicated,and there is an imbalance in the exhaust volume of each exhaust valve in the lateral centralized exhaust system.Based on this,this paper takes the standard three-lane immersed tunnel as the research background,starting from the vortex structure and flow loss effect,using the fluid dynamics analysis software FDS numerical simulation analysis to study the influence of smoke exhaust port parameters on smoke exhaust effect,and optimize the smoke exhaust port structure in the lateral centralized smoke exhaust system to reduce the smoke exhaust volume inhomogeneity of each exhaust port to achieve the purpose of efficient smoke exhaust.The main work and conclusions of this paper are as follows:(1)Based on the structural characteristics of the lateral concentrated smoke exhaust,the influence of different layouts,sizes and groups of smoke exhaust outlets on the smoke flow and smoke exhaust effect was explored.The numerical simulation analysis was carried out on the pressure difference,temperature field,velocity field and CO concentration of the smoke exhaust outlet around the layout of the smoke exhaust outlet.The layout of the smoke exhaust outlet with the best smoke exhaust effect was obtained.(2)Through the calculation of theoretical smoke emission,four kinds of smoke emission were selected for simulation analysis,and the optimal smoke emission was sought by combining the smoke temperature,smoke flow velocity,pressure difference and CO emission at the smoke outlet.The results show that based on the smoke exhaust efficiency,the smoke exhaust efficiency increases first and then decreases with the increase of smoke exhaust volume.The best smoke exhaust volume should be 180 m~3/s.(3)According to the concept of uniform smoke exhaust,through the flue gas flow energy equation,momentum equation and continuity equation,combined with the principle of static pressure complex method,the differential equation is established,and the relationship between the opening rate of the exhaust valve and the area of the exhaust valve and the pressure of the exhaust duct is established.(4)The changes of smoke flow velocity and smoke exhaust efficiency at the exhaust port are analyzed when the number of valve plates is different.The results show that the smoke flow velocity and smoke exhaust efficiency are sensitive to the change of the number of valves.When the number of valves in a single exhaust port is 5,no vortex area is formed in the exhaust duct,and the total exhaust efficiency is the highest.Through comprehensive comparison,the optimal design scheme of the number of valves is obtained.(5)By comparing and analyzing the smoke flow and smoke exhaust effect under12 kinds of smoke exhaust valve opening rate,it is found that setting smoke exhaust valve can obviously improve the defects of insufficient smoke exhaust and uneven smoke exhaust near the fire source.Taking the uniformity of smoke exhaust volume and smoke exhaust efficiency as the evaluation indexes,the optimal opening rate of smoke exhaust valve is obtained.The research results of this paper can provide a basis for the improvement of the lateral concentrated smoke exhaust theory,and provide a reference for solving the bottleneck problem of uneven flow velocity of the exhaust valve in one-way smoke exhaust. |
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