The Simulation And Control Of The Distribution Of Pollutants In Highway Tunnel

With the rapid development of China’s economy, the road transport undertakings have made great progress. The number of long highway tunnel is increasing. According to the National Bureau of Statistics, the number of national highway tunnel has reached 10,022 in 2012. The highway tunnel is a relatively closed underground space. The emission of vehicle exhaust pollutant(including carbon monoxide(CO), nitrogen oxides(NOX), hydrocarbons(HC) and carbon smoke particles) is difficult. The accumulated air pollutants inside the tunnel will affect the health and safety of drivers and passengers. In order to reduce the concentration of pollutants in the tunnel and ensure the safety and health, it is necessary for long highway to ventilate and control the concentration of pollutants.In this paper, taking Zhejiang Kuocangshan tunnel as an example, we calculate the emissions in the tunnel which CO and particulate matter depending on the traffic volume, vehicle category and other factors, and get the required amount of tunnel ventilation according to highway tunnel health standards.In this paper, we use Fluent to simulate this tunnel longitudinal ventilation and inside the tunnel pollutant concentration distribution and control strategy under different conditions. The main contents are:(1) When the normal operation of this tunnel, that is to maintain vehicle speed 60km/h, the influence of wind speed in the tunnel within a tunnel CO concentration distribution(2) When the blocked tunnel, the vehicle speed is maintained at 10km/h, the influence of wind speed in the tunnel within a tunnel CO concentration distribution.(3)When there is a vertical shaft, the tunnel is blocking or normal operation, the influence of the wind direction to CO concentration distribution.(4) Designed and built a air purification experimental device, and do experiments in the kuocangsan tunnel, analysis the effect of dust collection efficiency of the system as well as resistance.(5) Assess the position of bypass passage and wind speed in the tunnel when the air purification system is installed in the tunnel Kuocangshan.Research indicates:(1) The length of Kuocangshan tunnel is 7929 m. The CO emissions is 0.149626 m3/s, and the particulate matter emissions is 6.81127 m2/s. In order to meet health standards in the tunnel, calculating the required amount of wind is 657.6967m3/s and 939.4855m3/s according to CO emissions and particulate matter. So the required amount of the highway tunnel is 939.4855m3/s.(2) Under normal operating conditions, when the tunnel average wind speed is 1m/s, the distance of the tunnel entrance is 500 m before CO concentration reaching 250PPM; when the tunnel average wind speed is 3m/s, the distance of the tunnel entrance is 1050 m before CO concentration reaching 250PPM; when the tunnel average wind speed is 5m/s, the distance of the tunnel entrance is 2100 m before CO concentration reaching 250 PPM.(3)Under the blocked tunnel condition, when the tunnel average wind speed is 1m/s, the distance of the tunnel entrance is 275 m before CO concentration reaching 300PPM; when the tunnel average wind speed is 3m/s, the distance of the tunnel entrance is 600 m before CO concentration reaching 300PPM; when the tunnel average wind speed is 5m/s, the distance of the tunnel entrance is 650 m before CO concentration reaching 300 PPM.(4) When there is a vertical shaft, the tunnel is blocking or normal operation, the shaft is benefit for CO emissions; however, the effect of wind on the concentration of CO is different.; the same of direction of wind is more conducive to the CO emissions in the tunnel.(5) The dusty gas purification effect of the ESP system is significant. The system for PM2.5 and PM10 purification efficiency in the range of 95.0%- 80.0%, when the wind speed is 5 m/s ~ 10.0m/s. And the ventilation resistance is in the range of 121.0Pa ~ 388.0Pa.(6)When the air purification equipment is installed in Kuocangshan highway tunnel, we need to open a bypass at a distance of 3008 m at the entrance to the tunnel, the average wind speed in the tunnel is maintained at 4.74m/s. We can ensure that the concentration of contaminants at the exit of the tunnel meet health standards.