Simulation Research On Pollutants Distribution Characteristics Of Air Conditioning In Subway Station

In this paper,CFD software is used to simulate the spatial flow field,temperature field,and pollutant concentration field in subway platform and station halls.By searching for references and other methods,the first step is to generate pollutants(CO₂,PM_2.5,PM₁₀)at subway stations.Mechanisms,influencing factors and hazards were analyzed,and based on this,four return air ways were used to send double return intermediate return stations?model 1?and double return intermediate return station single delivery return?model 2?,single-send single-pass delivery of station halls corresponds to double-send intermediate return?model 3?,single-send single-sending of station halls corresponds to single-send single return of station?model 4?,indoor temperature and airflow velocity of subway stations,and pollutants distribution analysis and comparison.Draw the following conclusions:1.At the platform level,in the four air supply models,the CO₂ contents of the model 2and model 4 are basically the same,the volume fraction is below 0.1%,the model 1 is the highest,and the model 3 is the following.However,after a height of two meters,the situation changed and the model 2 CO₂ concentration increased sharply,exceeding the other three air supply methods,and the volume fraction was above 0.1%.The 1 CO₂ concentration was highest at each level of the station hall,followed by model 2 and model 4 at the lowest.The CO₂ volume fractions of model 1and model 2 at each height level exceeded the indoor air quality standard?GBT-18883-2002?.The standard value specified in 0.1%.2.The air supply method for single-send and single-pass delivery of the platform corresponding to a single station is more effective for dilution of CO₂ than other three types of air supply.3.In the four return wind models at platform level,the PM_2.5.5 of model 2 and model 4 at each height level is higher than that of model 1 and model 3,with model 4 being the highest and the lowest concentration reaching 28.34?g/m³.Model 1 had the lowest concentration at each level,and the highest concentration reached 21.81?g/m³.The concentration of the 3 and 4 in the station floor model was the highest at all levels,reaching 24.53?g/m³ or more.Model 2 was at all height levels.Is the lowest,the highest concentration of 18.92?g/m³.Although the four models have different effects on the dilution and purification of PM_2.5,since only the concentration of PM₁₀ is specified in China's"Code for Design of Metros"?GB50157-2003?,this article will refer to the public metro area of the US subway design standards.The PM_2.5 concentration requirements for the assessment of the subway station air quality,that is 35?g/m³,through the above analysis we can see that the four models meet this requirement.4.Particulate matter PM₁₀ In the four models,the PM₁₀ concentration in the station level model 4 was the highest at all height levels,with the lowest concentration reaching 36.95?g/m³,followed by the model 2,while the concentration of the model 1 at each height level was the lowest.The highest concentration was only 29.28?g/m³.The concentration of model 3 in the station hall was the highest,the model 4 was the lowest,and the model 2 had the lowest concentration in each height level.The lowest concentration of model 3 reached 36.53?g/m³,and the highest concentration of model 2 was only 20.82?g/m³,far below the national standard 150?g/m³.5.Through the analysis of the temperature,speed,CO₂,and the concentration distribution of CO₂ and two kinds of particles,it was found that the conditions under the four models can meet the requirements of the subway station for air quality.However,after comprehensive analysis,it was found that model 4 diluted and purified CO₂.The capacity is stronger than the other three types of air supply,while the model 2 is the best among the three methods of air return in terms of particle dilution and purification.