Research And Optimization Of Pollutant And Thermal Comfort In Urban Air-Conditioned Bus

With the continuous development of urban construction in our country,the innovation of transportation is changing rapidly.The use of air conditioned buses has become quite common.Nowadays,environmental pollution is at the cusp.The air quality in buses has become a hot topic of concern.The air conditioned bus is well closed,and the air in the car is mainly adjusted and improved by the air conditioning system.The new wind enters the car through the air conditioning system,diluting the polluted gas in the car and bringing it into the car room with the air flow organization.In this paper,the thermal comfort of the human body and the concentration of CO2 in the air conditioned bus are studied.Based on theoretical analysis,based on the physical properties of gaseous pollutants,the characteristics of temperature and wind speed and the diffusion and distribution of gaseous pollutants under the action of air distribution in air conditioned vehicle are studied.The environmental quality measurement model is applied to analyze the migration and diffusion of gaseous pollutants in the vehicle compartment.By establishing the three-dimensional convection diffusion control equation of gaseous pollutants,combined with the numerical simulation method of turbulent flow,the CO2 distribution in the vehicle compartment is studied.A line bus in Shenyang is selected as the research object.Based on different seasons and different time periods,the TSI9555-P ventilation tester and TSI7545 air quality detector are used to monitor the temperature,wind speed and CO2 concentration at different locations in the air conditioned bus.The results show that the average concentration of CO2 in the summer peak is above 0.2%,which is more than the acceptable limit of 1500ppm in the human body.At the low peak period,the number of passengers in the car was about 30 people,the concentration of CO2 was between 0.06～0.08%,and the people had no obvious discomfort.The concentration of CO2 in the winter peak and low peak period was generally in 0.2～0.4%,which exceeded the standard seriously.The use of CFD technology,building a geometric model of the air-conditioned bus,in the car air quality survey results as the basis for the two seasons of winter and summer,the car loaded with passengers and a small amount of indoor temperature,wind speed and the concentration of CO2 in two cases of numerical simulation.The results showed that when there were a small number of passengers in the summer,the CO2 mainly concentrated in the front end of the car room,and the air quality at the rear part of the car was better.When the load was full,CO2 was concentrated in the middle of the car compartment,and the CO2 concentration in the vehicle was higher.The average mass fraction was 0.2%,which was beyond the design standard value.The effect of vehicle ventilation in winter is poor.When a small number of passengers are there,the CO2 mass fraction can reach 0.4%.When the load is full,the CO2 mass fraction is over 0.5%.The concentration of CO2 in the bus at present exceed the standard in winter and low temperature inside the car,put forward two different optimization scheme of adding return air or to send back to the air flow organization,were simulated by using Fluent software,two kinds of optimization results show that the airflow inside to form the optimization effect under the program back to good,summer and winter load under the condition of high concentration of CO2 breathing can be reduced to about 0.05%,has met the interior air quality standards.