Evaluation And Optimization Of Underground Garage Ventilation System With Rank 2 Personnel Shelter

In recent years,more and more underground garage and civil air defense projects are being built.The design of the ventilation system is very important in the construction as it relates to the usual garage air quality and safety of masking people in wartime.The evaluation and optimization of ventilation system performance has very important significance.In this paper,a case study is conducted on the underground garage with rank 2 personnel shelter.The air flow organization of different ventilation systems in underground garage is analyzed,distribution of C02 and 02 in the protection unit in wartime are simulated and the distribution of pollutants in the air-lock when overpressure exhaust is shown,witch have some reference values for the design of underground garage ventilation system with rank 2 personnel shelter.The case model of original ventilation system:wind pipe mechanical ventilation + natural wind of underground garage,length of which is 62m,width 35m,area 1940 m2,was established with airpak.What's more,three optimization schemes was established,wind pipe mechanical ventilation + mechanical wind,inductive ventilation and mechanical wind,inductive ventilation and natural wind.During simulation,air supplied is five times the volume of the building,exhaust volume six times.Through the analysis of data that CO distribution and velocity vector of 1.5m cross-section,CO distribution 11 Y-sections,values of CO average concentration and maximum concentration in 30 1.5m-cross-section,the results are following:(1)in the original ventilation system,the average concentration of CO is 38mg/m3,the maximum concentration of CO is 148.3mg/m3 on 1.5m-cross-section,which show high and uneven CO concentrations,and the system of wind pipe mechanical ventilation + natural wind need to be optimized.Among the four conditions discussed in the paper,the overall level of pollutants is lower,and both average concentration and maximum concentration of CO are lower too in the system of inductive ventilation and mechanical wind.Furthermore,Whether 2m3(P.H)fresh air can meet shelter requirements in wartime is verified in the paper and how distribution of the air volume in antiknock units influences O2 and CO2 concentrations in the protection unit are analyzed.The model of underground garage is transformed to the model of rank 2 personnel shelter using airpak whose shelter area 1360 m2.Afer the analysis of datas that O2 and CO2 distribution,the results show that the lowest concentration of O2 was 19.32%,and the highest concentration of CO2 was 1.53%in 1.1m cross-section which can meet demands for the masking personnel in the protective.The distribution of fresh air volume according to the number of people in every antiknock cell is not conducive to the distribution of O2 and CO2 but does well when increasing fresh air volume appropriately in the antiknock cell upstream of air flow direction.Lastly,in order to optimize air quality in gateway,the model of gateway was established using gambit and air flow organization in air-lock was simulated with fluent when wind curtain were set at bottom or top of the door adjacent to the out door or no wind curtain was set.After the analysis of cl2 distribution,the result show that the curtain at the bottom of the door is more effective to block horizontal airflow and disturbance in the gas channel is small.Through the simulation of time it took to discharge cl2 in gateway after closing door,we drew the following conclusion when speed of curtain rose,the time decreased.It have no relation to the length of time during which the door is open.