Research On Mixture Mechanism Of Exhaust Air With Inlet Air In Small Space Road Tunnels And Its Countermeasures

More and more tunnels are equipped with longitudinal ventilation systems. Under the way of longitudinal ventilation, the circulation wind will be formed at the entrance of tunnels, such as manifold tunnels, small space tunnels and double-arch tunnels. Under the action of circulation wind, the exhausted air from one tunnel will be partially even completely mixed with the fresh air which will be sent into adjacent tunnel. The phenomena of mixing wind brings the research topic on effect of tunnel ventilation caused by tunnel space and wind speedThe research status of mixing wind in the ventilation of small space tunnels is introduced first. A numerical model is proposed based on the characteristic of Baziling tunnel in the Shanghai-chengdu expressway and the mechanism of the diffusion of the exhausted air from way out of tunnel and the influence caused by the circulation wind in the ventilation of adjacent tunnel are simulated by the FLUENT software. With the numerical results of the research work, a thorough understanding of the mechanism of the diffusion of circulation wind has obtained. Furthermore, the relationship of tunnel air mixture with tunnel space and velocity are set up.Based on the mixture effect of small space tunnels, engineering measures to reduce the effect are suggested to build intermediate wall, stagger the way out of tunnels and construct lateral tunnels to discharge exhaust air. The engineering measures to improve the mixture of exhaust air are also simulated in 3D. The results shows that stagger the way out of the tunnels have good effect on. The conclusions from the research work will be applied to Baziling tunnel, Miaoya tunnel and Qishucao tunnel in the Shanghai-chengdu expressway.