Simulation Research Of Vehicle Pollutant Emissions And Dispersion In Urban Street

With the rapid growing of vehicle population, vehicle emissions have become a major source of urban air pollution. The street canyon formed between tall buildings and streets is very general, and the exhaust of motor vehicles accumulates in the street canyon, which does great harm to the travelers who directly exposed in the atmosphere and environment around. In this paper, according to the new features of air pollution, based on the field survey, the author connects the knowledge of environment science, transportation engineering and hydrodynamics and uses the result of theoretical calculation, the microscopic traffic simulation technology and the numerical simulation method to carry out the study of local air pollution in cities, which could provide data basis and technical support for the improvement of urban environment and residents’ life quality. Main work and conclusions are as follows:(1) Organization personnel conducted field investigation and study in the east side road of Baotu Spring Park and surrounding roads in Jinan, and we found that the motor vehicle within research sections has the characteristics of long delay time, low average speed, large amount of emissions and high fuel consumption.(2) This thesis takes the section near the east gate of Baotu Spring as research subject, quantity of pollutant discharged and overall fuel consumption as optimal indexes, and with the help of microscopic traffic simulation technology, simulates and optimizes the traffic signal timing according to the results of field surveys and theoretical calculations. The result shows that after the optimization of time assignment of traffic signals, the average speed of motor vehicles in the section studied has increased by24%, the overall fuel consumption has reduced by17%; the vehicle emissions also has a sharp falloff, among which CO emissions have reduced by7%; the goal of easing traffic congestion, improving the environment and saving energy and reducing emission has been achieved basically.(3) The author uses the numerical simulation method to study the pollutant effect on the pedestrians. In this study, the author combined the standard k-ε turbulence model and component transport equation to research the intersection and compared with the wind tunnel test data to verify the correctness of the numerical simulation method. By researching the intersection of Baotu Spring Road and Quan Cheng Road, the author used the numerical simulation method to study the distribution of the pollutant concentration field in the intersection and analyzed the influence of different wind direction to the pollutant diffusion, Through the research we found that the concentration of pollutants in leeward side and block center is much higher than that in the windward side in street canyon; wind that is unparallel to street axis has decisive influence on pollutant proliferation, because wind with an angle to the street axis can make strong horizontal vortex at the intersection, causing the pollutants around relatively concentrated, thus forming a high concentration area of pollutants. Also we found, under the selected three kinds wind direction, the area near the north gate of Baotu Spring Park has a large amount of pollutants accumulation, so pedestrians and traffic policemen should try to avoid staying in high polluted area for too long time.(4) We also analyzed the influence of traffic signal control on motor vehicle emissions and found a very big difference of pollutants concentration distribution at intersection in two continuous phase time of one signal cycle. Combining with the actual traffic situation, we concluded that, this is mainly determined by the intensity of the emission of pollutants and height of the buildings.