【正文】 and belongings (Chow and Li, 1999。 Modic, 2020。 Carvel et al., 2020). The characteristics of emergency situation have been well investigated, but there have been few studies in air distribution of sideplatform in normal conditions. The development of large capacity and high speed puter and putational fluid dynamics technology makes it possible to use CFD technology to predict the air distribution and optimize the design project of subway ventilation system. Based on the humanoriented design intention in subway ventilation system, this study simulated and analyzed the ventilation system of existent station and original design of rebuilt stations of Tianjin subway in China with the professional software AIRPAK, and then found the optimum ventilation project for the ventilation and structure of rebuilt stations. 2. Ventilation system Tianjin Metro, the secondlybuilt subway in China, will be rebuilt to meet the demand of urban development and expected to be available for Beijing 2020 Olympic Games. The existent subway has eight stations, with a total length of km and a km average interval. For sake of saving the cost of engineering, the existent subway will continue to run and the stations will be rebuilt in the rebuilding Line 1 of Tianjin subway. Although different existent stations of Tianjin Metro have different structures and geometries, the Southwest Station is the most typical one. So the Southwest Station 外文資料翻譯 第 3 頁 model was used to simulate and analyze in the study. Its geometry model is shown in Fig. 1. . The structure and original ventilation mode of existent station The subway has two runlines. The structure of Southwest Station is, length width height = m(L) m(W) m(H), which is a typical sideplatform station. Each side has only one passageway (length height = m(L) m(H)). The middle of station is the space for passengers to wait for the vehicle. The platform mechanical ventilation is realized with two jet openings located at each end of station and the supply air jets towards train and track. There is no mechanical exhaust system at the station and air is removed mechanically by tunnel fans and naturally by the exits of the station. . The design structure and ventilation of rebuilt station The predicted passenger flow volume increase greatly and the dimension of the original station is too small, so in the rebuilding design, the structure of subway station is changed to, (length width height = 132 m(L) m(W) m(H)), and each side has two passageways. The design volume flow of Southwest Station is 400000 m3/h. For most existent stations, the platform height is only m, which is too low to set ceiling ducts. So in the original design, there are two grille vents at each end of the platform to supply fresh air along the platform length direction and two grille vents to jet air breadthways towards trains. The design velocity of each lengthways grille vent is m/s. For each breadthways vent, it is m/s. Under the platform, 80 grille vents of the same velocity ( m/s, 40 for each platform of the station) are responsible for exhaust. 3. CFD s