Study On Natural Ventilation Of Urban Tunnel With Upper Vents

The first use of urban tunnel with upper vents is HongXing road tunnel in ChengDu. Because the urban tunnel with upper vents can exhaust polluted air and get fresh air through the upper vents along the tunnel, the pollution of environment in the outlet can be alleviated. And urban tunnel with upper vents maybe is more ascendant than mechanical ventilation in fire smoke extraction. So the urban tunnel with upper vents will be the new kind of urban tunnel. But from now on ,there is nothing rules about this kind of tunnel, so the study of natural ventilation and fire smoke flow characteristics becoming necessary.This paper make an analysis of natural ventilation on the base of continuity and the energy conservation law, after the corresponding simplified, build its one-Dimensional mathematical model. Discuss when the number of vehicles running in the tunnel and the location and size of openings changes, the corresponding changes on the flow of the tunnel airstream and the distribution of the concentration of harmful gases. Through the study, we can see increasing the vents area and decreasing the distance between vents is good for the tunnel environment. When the traffic in the tunnel blocked, hot pressure will make natural ventilation in the urban tunnel with upper vents, so the CO concentration in the tunnel without vents is higher than the tunnel with upper vents.Establishing corresponding actual fire simulation computer models with CFD, and build the three-Dimensional model with STAR-CD, study the diffuse rates the temperature of smoke distribution in the tunnel and the security of the people near the fire, when the distance from fire to the first vent is 60m and 130m.