| The tunnel is a relatively closed environment,and the exhaust gas from vehicles is limited in a limited space,which is difficult to circulate in a short time,which will inevitably affect the normal operation of the tunnel and the personal safety of drivers and passengers.By the end of December 2019,the number of motor vehicles in Suzhou has reached 4.822 million,including 4.177 million vehicles,ranking among the largest cities in China.The rapid increase of car ownership has a great impact on the traffic environment in the tunnel.In order to ensure the safety of tunnel operation and the health of drivers and passengers,it is necessary to conduct in-depth study on the diffusion law of vehicle exhaust gas in the tunnel and the longitudinal ventilation mode in the tunnel.Firstly,the paper introduces the current situation of automobile exhaust diffusion and tunnel ventilation at home and abroad,as well as the relevant design standards and specifications,and makes theoretical analysis on the Gauss line source diffusion model of automobile exhaust,the design concentration of pollutants,the determination method of main control pollutant emissions and air demand,tunnel jet fan and other issues.Secondly,according to the service level of road hierarchy,microscopic traffic simulation software VISSIM simulation are used to get the average speed of vehicle under different conditions,and then select a tunnel in suzhou,using the gaussian source diffusion model respectively in different speed,different wind speed and different type ratio under the condition of the concentration of CO,using the CFD software two-dimensional model for numerical simulation of the tunnel,the tunnel car exhaust,the dispersion characteristics under various conditions.Finally,when the concentration of pollutants in the tunnel exceeds the concentration limit in the relevant regulations,it is necessary to conduct mechanical ventilation inside the tunnel.According to the discharge amount of pollutants in the tunnel,the fresh air quantity needed to dilute the tunnel is determined,and the number of jet fans needed to control the concentration of pollutants in the tunnel within the limit is calculated by the pressure balance principle in the tunnel.This topic in the tunnel of the spread of the automobile exhaust CO concentration and the longitudinal flow inside the tunnel ventilation requirements as the main research objective,and based on this,advances the pollutant control measures with pertinence,and hope for the construction of the tunnel and provide reference for safety operation,for the relevant departments to effectively control tunnel of motor vehicle pollution,improve the air environmental quality to provide decision basis,good use of practical value. |
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