Numerical Analysis of CO Concentration Distribution on Extraction Ventilation Type Tunnel

The highway tunnel is a relatively closed space, then large amounts of motor vehicle exhaust emissions, especially CO, resulting in air pollution in tunnel. The project construction cost, operation cost, and pollutant concentration distribution in tunnel are most dependent on ventilation scheme. Usually have air extraction and inflatable type ventilation system. In this paper, a numerical simulation based on two-phase flow is used to study the effect of double air extraction ventilation system to CO concentration distribution in large tunnel. The method can effectively track the gaseous diffusion and the results show that the CO concentration is lowest in the middle area of two vents and the exit area of tunnel. The highest area of CO concentration located in vents below area and the middle area of tunnel.