| With the vigorous development of urban rail transit,the environmental control system as an important part of rail transit is also progressing.At present,the screen door system is a commonly used environmental control system.When the screen door is closed,there will be a small amount of leakage wind at the gap of the screen door due to various factors.When the screen door is opened,a large amount of leakage wind appears at the sliding screen door,and a large amount of heat exchange between the air in the tunnel and the air on the platform causes the temperature field and velocity field of the platform to change,which affects the thermal environment of the platform and the comfort of the personnel.In this paper,the platform area of Xi’an Metro BIANJIACUN Station is taken as the research object.The numerical calculation models of the platform public area are established by the existing mixed ventilation mode and the new ventilation mode-attached ventilation.Based on CFD simulation,the influence of leakage wind generated by the gap on the thermal environment of the platform in summer is analyzed.The influence of screen door opening on different sides(upper / lower line side)on the summer thermal environment of the platform is discussed.The effects of different leakage wind speed,different tunnel temperature and different opening time of the shield door on the thermal environment of the platform in summer were studied when the shield door on the down line side was opened only.The factors affecting the thermal environment of the platform when the screen doors on both sides are opened at the same time are analyzed by orthogonal test.Finally,the disturbance effect of the opening and closing of only one side of the screen door and the opening and closing of both sides of the screen door on the thermal environment of the platform is discussed.The temperature field and velocity field of the platform under two ventilation modes(mixed ventilation and attached ventilation)were compared and analyzed.The temperature non-uniformity coefficient,velocity nonuniformity coefficient,air distribution characteristic index(ADPI)and relative thermal index(RWI)were selected to evaluate the thermal environment of the platform.The conclusions are as follows:(1)Under the two ventilation modes,the air leakage caused by the gap has little effect on the thermal environment of the platform when the platform screen door is closed.The average temperature of each typical section is only 0.3～0.5°C higher than that when the air leakage of the platform screen door is ignored,indicating that the application of the platform screen door effectively blocks the heat exchange between the tunnel air and the platform air.(2)Under the two ventilation modes,the leakage wind generated when the screen door is opened has a greater impact on the thermal environment of the platform.When only the shield door on the down line side is opened,the greater the leakage wind speed of the shield door,the worse the comfort of the platform;with the increase of tunnel temperature,the ADPI value under mixed ventilation mode is less than 40%,and the ADPI value under attached ventilation mode gradually decreases from 46.3% to 40.2%.With the increase of the opening time of the screen door,the ADPI value decreased from39.0% to 32.3% under the mixed ventilation mode,and the ADPI value decreased from57.9% to 38.4% under the attached ventilation mode.(3)Through the range analysis of three factors(leakage wind speed,tunnel temperature and shielding door opening time),the results show that when the shielding doors on both sides are opened at the same time,the most influential factor on the thermal environment of the platform is the tunnel temperature,followed by the shielding door opening time,and the influence of leakage wind speed is the smallest.(4)With the increase of shield door opening time and tunnel temperature,the time required for the thermal environment of the platform to return to the initial state increases.When only one side of the screen door is opened and closed,taking the tunnel temperature of 32°C and the screen door opening for 30 s as an example,the time required for the thermal environment of the platform to return to the initial state under the attached ventilation mode is 27 s shorter than that of the mixed ventilation.When the shield doors on both sides are opened and closed at the same time,taking the tunnel temperature of32°C and the shield door opening for 30 s as an example,the time required for the thermal environment of the platform to return to the initial state under the attached ventilation mode is 52% shorter than that of the mixed ventilation.It shows that the platform can better maintain the stability of its internal thermal environment by the attached ventilation mode. |
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