Numerical Simulation And Optimization Design Of After-Fire Ventilation System In The Cable Compartment Of The Utility Tunnel

With the shortage of land resources,it is proposed to construct the urban underground utility tunnel to make full use of the limited underground space.The utility tunnel is completely under the ground,and belongs to a semi-enclosed structure.Therefore,the air circulation is poor.Besides,itself and the cable compartment,the heat compartment,the sewage compartment,and the gas compartment will generate heat and produce toxic and harmful gases.These problems poses a threat to the utility tunnel itself and are not conducive to the inspection and maintenance for maintenance personnel.Among the various types of compartments of utility tunnel,the cable compartments bear great fire risk.At the same time,electricity is the energy and blood of the city and plays an important role in economic development and people’s lives.Once the cable fire accident occurs,it will seriously affect our daily life and production.Thus,it is necessary to conduct the research and analysis on the fire process and the smoke exhaust after the fire in the cable compartment,so as to optimize the ventilation system and reduce the accident losses as much as possible.Based on the actual size of an utility tunnel in Xi’an,an experimental model was established by using the software PyroSim in this paper,which conducted a simulation study on the fire.First,the case 1(the ventilation system was closed)was simulated to observation the situation of fire development,smoke diffusion and temperature changes during the fire,and then determined the reasonable time to open the ventilation system.Secondly,taking into account the influence of the ventilation pavilion height on thesmoke and harmful gas exhausting after fire in the cable compartment,cases 2 to 11 were designed.Among them,the air inlet pavilion heights of the cases 2 to 8 were changing,and the remaining conditions were same.The air outlet pavilion heights of the cases 2,9,10,and 11 are changing,and the remaining conditions are same.Through simulation analysis,it can be concluded that condition 2 is the best solution.Thirdly,considering the the influence of the shutter vent on the smoke and harmful gas exhausting after fire in the cable compartment,cases 12 to 21 were designed.Among them,the air inlet shutter vents of the cases 12 to 18 were changing,and the remaining conditions were same.The air outlet shutter vents of the cases 12,19,20,and 21 are changing,and the remaining conditions are same.Through simulation analysis,it can be concluded that the optimum design of the shutter air outlet is working condition12.Finally,through summarizing the effect of these two factors on the smoke and harmful gas exhausting after fire in the cable compartment,a more secure,more economical and more effective design scheme was obtained by optimizing the ventilation system.