Study On Air Quality And Pollutant Distribution Characteristics In Subway Cars

With the increase of urban population density,people's demand for public transportation has increased.The subway has become an indispensable means of transportation for people's daily travel because of its advantages of convenience,speed and large passenger capacity.Metro rail transit is a relatively closed underground space.The indoor environment is only regulated by the air conditioning system.At the peak of the passenger flow,the pollution sources in the cabin increase,and the ventilation of the air conditioning system is insufficient.People who are in it will have irritability,dizziness and other symptoms.Therefore,air quality is an important factor affecting the comfort of the cabin environment.It is of great practical significance and practical value to study the air quality in the subway car.This paper uses questionnaire survey,on-site measurement and numerical simulation to analyze the air quality in the subway car.Firstly,the air quality questionnaire survey was conducted on the passengers in the train,and the passengers' subjective evaluation of the ambient air quality of the cabin was obtained.Then according to the research results,the pollutants in the compartments of different time periods were tested and analyzed,and the variation of pollutants with time was analyzed.Then,the distribution of pollutant concentration in the compartment under different seat densities was analyzed by numerical simulation,and the distribution of pollutants in space was explored.Finally,the calculation model of the pollutant concentration of the cabin is established.Based on the efficiency of the fresh air volume and the air filter,the suggestions for improving the air quality of the subway compartment are proposed.The specific research contents are as follows:?1?Subjective questionnaire survey was conducted on passengers in Qingdao subway trains.According to the survey results,passengers have a more inclusive attitude towards the air quality in the train compartment,and the acceptance rate is higher,but the overall satisfaction level is not high.There is still room for improvement in air quality.?2?Taking Qingdao Metro as the research object,the concentration of pollutants in the subway car was tested.It is known from the test results that the CO₂ concentration and the particulate matter concentration during the peak period of the passenger flow are greater than the off-peak period,and the CO₂ concentration in the vehicle area.Above the door area,the particulate matter concentration is lower than the door area.?3?Simulated the distribution of pollutant concentration in the compartment under different seat densities.It can be seen from the simulation results that the density of the seat is increased and the airflow is short-circuited,resulting in a large wind speed in the upper part of the compartment.There is discomfort;at the same time,the concentration of pollutants in the compartment increases,and the pollutants in the lower part of the compartment cannot be discharged in time due to the influence of the airflow,which is likely to cause accumulation and adversely affect the sitting passengers.?4?Based on the primary air return air-conditioning system of the subway car,the calculation model of the CO₂ concentration and the particulate matter concentration of the compartment is established.The filtration efficiency of the fresh air volume and the air filter is taken as the control variable,and the air quality optimization scheme for improving the subway compartment is proposed.