地铁环境内的通风效率对室内空气品质的影响

维持地铁环境中的空气清洁对乘客来说是非常重要的。尽管地铁站的屏蔽门（PSD）可以很好地改善地铁站内空气品质,但地铁隧道内的空气品质却仍然很差,隧道内CO2浓度和颗粒物（PM）值均较高。增加列车运行的频率和数量,均会导致地铁环境内的空气品质变差。因此,为获得更好的空气质量,地铁隧道的通风系统需要进一步改进。数值分析是一种有效的方法,可用来分析地铁双轨隧道通风系统的性能。本文对位于韩国首尔的地铁双轨隧道系统进行了数值模拟,采用ANSYS CFX软件对列车正常运行时隧道内的气流进行了非定常计算。分别针对一辆列车在隧道里运行,或者两辆列车同时运行时,对隧道内的气流进行了模拟研究。当所有的竖井用于自然通风时,分析了隧道里的活塞效应。结果表明,竖井送风对隧道内污染气体稀释以后,通过机械通风井排出;当双轨隧道内仅有一辆列车运行时,供气量和排气量是平衡的;当同时有两辆列车相向运行时,隧道内的污染空气浓度很高,且竖井里没有电力供应时,所有的竖井用于自然通风。车站门被打开时,停留在隧道内的污染空气就会进入车站站台。

Ventilation Efficiency in the Subway Environment for the Indoor Air Quality

Clean air in subway station is important to passengers.The Platform Screen Doors （PSDs） can improve indoor air quality in the subway station; however the air quality in the subway tunnel is degraded. The subway tunnel has high CO2 concentration and indoor particulate matter（PM ） value. The Indoor Air Quality （IAQ） level in subway environment degrades by increasing the frequency of the train operation and the number of the train. The ventilation systems of the subway tunnel need improvements to have better air-quality. Numerical analyses might be effective tools to analyze the performance of subway twin-track tunnel ventilation systems. An existing subway twin-track tunnel in the metropolitan Seoul subway system is chosen for the numerical simulations. The ANSYS CFX software is used for unsteady computations of the airflow inside the twin-track tunnel when the train moves. The airflow inside the tunnel is simulated when one train runs and two trains run at the same time in the tunnel. The piston-effect inside the tunnel is analyzed when all shafts function as the natural ventilation shaft. The supplied air through the shafts is mixed with the pollutant air in the tunnel. The pollutant air is exhausted by the mechanical ventilation shafts. The supplied and discharged airs are balanced when only one train runs in the twin-track tunnel. The pollutant air in the tunnel is high when two trains run simultaneously in opposite direction and all shafts functioned as the natural shaft cases when there are no electrical power supplies in the shafts. The remained pollutant air inside the tunnel enters into the station platform when the doors are opened.