Research On Pollutant Emission And Dispersion Characteristics Of Urban Tunnel Based On Traffic Characteristics

In recent years,with the large-scale use of underground space,more and more tunnels will be built in the city.As the city tunnel is relatively closed,a large number of toxic and harmful substances discharged by the vehicle during driving will pose a major threat to the health of the human body.Therefore,studying the emission and diffusion laws of pollutants in urban tunnels has guiding significance for ventilation design and installation of ventilation equipment in urban tunnels.This thesis uses COPERT IV model to calculate the emission factors of different models including CO,NOx and HC pollutants.A linear regression model was used to establish a model for the relationship between pollutant emissions and driving speed in urban tunnels.The reliability of the model was verified by the measured data.The pollutant discharge model for bicycles was applied to a typical urban tunnel.The calculation of the total amount of pollutants emitted by motor vehicles in urban tunnels shows that the concentration of pollutants in the tunnel exceeds the standard when the tunnel encounters peak traffic times and local congestion.Indepth analysis of several widely-used traffic flow parameter models,comparing the selection of the Greenshields mathematical model to study the relationship among the speed,traffic volume,and density in urban tunnels;based on the characteristics of the traffic environment of urban tunnels,The characteristics of pollutant emission factors in each section of the tunnel were studied separately from traffic volume and density,and the traffic volumepollutant emission factor model and density-pollutant emission factor model of each model of urban tunnel sections were established.A linear regression method was used to verify the relationship between traffic flow characteristics and pollutant emission factors in the tunnel and to ensure the accuracy of vehicle emission factors.This provided a theoretical basis for pollutant distribution and purification technologies.Introduce the atmospheric advection equation in which the vehicle exhaust gas diffuses inside the urban tunnel.By simplifying the mathematical formula,the longitudinal distribution formula of the pollutant concentration in the tunnel when using vertical ventilation and no mechanical ventilation is obtained;the equations can be used to obtain the different traffic conditions of the urban tunnel.