Influence Of Piston Effect On Ventilation Performance And Utilization Strategy In Subway Station With Platform Screen Doorin Chongqing

With the rapid growth of China's urban scale,rail transit represented by the subway has been vigorously developed,but at the same time,the problem of high energy consumption of the subway HVAC?heating,ventilation,and air conditioning?system has become increasingly prominent.An important difference between subway station and other underground public building HVAC system is the influence of piston effect.In recent years,the feasibility of shutting down over tunnel exhaust fan and under platform exhaust fan?OTE/UPE?in platform tunnel has been verified and began to be used in Chongqing subway stations.The exhaust fans no longer have impacts on the piston wind and platform screen door leakage quantity,so the results of the previous study on subway station ventilation performance may not be in line with actual situation.Meanwhile,there are few studies focus on the quantity and utilization of train-induced airflow from the exits of the station under the influence of piston effect.Therefore,based on measurement and SES ventilation network model,combined with the fresh air demand,this paper explores influence of piston effect on ventilation performances,the influencing factors and the strategies to rationally utilize train-induced fresh airflow.In this paper,three typical platform screen door subway stations were field measured in different seasons and different mechanical ventilation modes.Through the analysis of the train-induced fresh airflow volume and its variation regularity of the exits in the mode of no mechanical ventilation mode?that is,all the mechanical fans were closed?,it is found that the airflow volume of the exits can meet the fresh air demand in the early stage or the usual period of station,but it cannot meet the demand of long-term stage and the rush hour.Meanwhile,it is pointed out that the main factors affecting the quantity of train-induced fresh air are train operation and mechanical fan operation mode.Aiming at the running state of the train,An SES ventilation network model of station C is established.And the quantitative relationship between the maximum running speed,the departure frequency,the arrival interval and the train-induced airflow is calculated and analyzed.It is found that departure frequency has the greatest influence on the amount of train-induced airflow,followed by the arrival interval.The train-induced airflow volume increases linearly with the increase of the maximum running speed of the train.It has a cubic polynomial relationship with the train starting frequency,and increases firstly and then decreases with the increase of train arrival interval.As for the mechanical fan operation mode,under different fan operation modes of the ventilation season season and the cooling season,the train-induced airflow,the station temperature,relative humidity and the CO₂ concentration are continuously monitored.From the perspective of fresh air supply and demand,the difference between the fresh air volume in the public zone of station and the controlled environment?temperature and relative humidity,CO₂ concentration?in different public ventilation modes are quantitatively compared.It is proposed that cancel the small fresh air,using all-return mode,in air-conditioning season,and shut down the mechanical ventilation or use single-row mode in ventilation season.Finally,the strategy analysis of the energy efficiency scheme of mechanical fan is carried out.The operation scheme of C station fan is refined,and through the simulation of three modes of no mechanical ventilation,opening an exhaust fan and opening two exhaust fans,the critical outdoor temperature corresponding to the exclusion waste heat demand in the station is obtained,and the specific control strategy is given.It is proposed to turn off the mechanical fan when the maximum temperature of outdoor day is less than21?,and to turn off the small fresh air fan in the cooling season,and the energy of the annual ventilation and air conditioning system is calculate.