Study On Natural Ventilation Potential Of Guangzhou Metro Station With Fully Enclosed Platform Screen Doors

With the wide application of the full enclosed screen door system in metro station,the energy-saving demand is more and more significant.The reasonable utilization of the fresh air at the entrance and exit of the subway station can effectively improve the air quality in the subway station,replace the mechanical fresh air system or reduce the mechanical fresh air volume in summer and transition season,and cancel the exhaust fan in the public area of the station or reduce the operation time of the exhaust fan in winter.At present,the design of the environmental control system of the subway station with totally enclosed screen doors lacks the full understanding of the fresh air at the entrance and exit,and the fresh air at the entrance and exit can not be reasonably used in the design and operation of the early ventilation and air conditioning of the subway station.Therefore,it is necessary to analyze the flow characteristics and the influencing factors of the fresh air at the entrance and exit,and study the effectiveness of replacing the mechanical fresh air system with the fresh air at the entrance and exit In order to achieve the goal of air conditioning energy saving.In this paper,an island subway station in Guangzhou is taken as the research object,and the following research work is mainly carried out for the natural ventilation at the entrance and exit of the station:Based on the actual measurement of the subway station,the inlet and outlet air conditions,outdoor CO₂concentration changes,temperature and humidity and CO₂concentration changes in the public area of the subway station under different seasonal conditions（small fresh air in air conditioning season,fresh air in transition season and total ventilation in winter）are obtained.Through the actual measurement of the subway station,we can fully understand the natural ventilation condition and the change of the hot and humid environment in the station,and find that the air intake at the entrance and exit can fully meet the fresh air demand of the personnel in the station,and provide basic data and parameters for the establishment of the multi area ventilation network model of the subway station.Based on the measured data of the subway station in each season,the multi area ventilation network model of the subway station is established by using the software contam.The natural air volume at the entrance and exit of the station,the air volume at the stairway between the station hall and the platform,and the leakage air volume of the screen door are simulated and calculated in each season,and the air circulation law of the public area of the whole subway station is obtained.According to the factors that affect the natural ventilation of subway station:the wind pressure caused by outdoor wind speed and direction,the heat pressure caused by indoor and outdoor temperature difference,the piston effect caused by the train running and the negative pressure of screen door caused by the track exhaust hot air blower,this paper analyzes one by one to explore the impact on the natural ventilation of the entrance and exit of subway station,and clarifies the impact of each factor on the natural ventilation of subway station And the degree of impact.By using the method of setting CO₂diffusion source in the public area of metro station with contam software,the unsteady state simulation of the change of CO₂concentration in the public area of metro station under different passenger flow is carried out,and the effectiveness of replacing the mechanical fresh air system in the station with fresh air at the entrance in the near and long term conditions is studied respectively.The results show that in the air-conditioning season and transition season,the environmental control system of metro station adopts the mode of no mechanical fresh air.In winter,when the mode of no mechanical exhaust is adopted,the fresh air at the entrance and exit alone is enough to meet the fresh air demand of the station personnel under the recent working conditions.The carbon dioxide concentration of the public areas of the station hall and platform is below 1500 ppm.However,when the passenger flow reaches the long-term peak level,the station still needs to open the mechanical fresh air system.