Three-Dimensional Numerical Simulation Study On Fire Ventilation In Highway Tunnel By Shaft

Zhongnanshan extra-long highway tunnel in Qinling is designed as double tunnels and single traffic mode, which is with three shafts and longitudinal ventilation control. Because there are many ventilating shafts and passage ways linking up the two tunnels, with ventilation ducts and ventilators in the extra long highway tunnels, the ventilation technology of the tunnel is highly complex. When the tunnel is on fire, the different ventilating plans effect the development of fire and controlling of the smoke much. In this paper, the author takes Zhongnanshan extra-long highway tunnel as the researching object to simulate tunnel fire with vary ventilation plans when the fire occurs at different location near the exhaust-shaft.The paper presents the methods and researching condition of tunnel fire ,the characteristic of emergency ventilation, and the system of rescuing and putting out fire in tunnels. Then, based on the conservation laws, the three-dimensional physical and mathematical model of the smoke movement in tunnel fire was established specially for longitudinal ventilation in the tunnel by shaft using STAR-CD software. And finite volume method was used to discretize the governing equations and the SIMPLE algorithm was employed to solve the discrete equations. We get the distribution rules of velocity, temperature and pressure by dealing with the situations in different ventilated velocity, different fire locations, different combinations between axial-flow fans in ducts and jet fans in tunnel, and in which delivery shaft and the other tunnel' s exhaust are on or off.By analyzing the simulated results, we conclude the characteristic of smoke velocity, temperature and pressure, and their changing disciplines with 2m/s and 3m/s ventilating velocities whichare recommended by "highway tunnel ventilation, lighting design standard" (JTJ026. 1-1999);and the influence of different ventilated velocity and different ventilating plan is analyzed;the formation and affect of shaft' s "chimney effect" are also discussed. At last, taking into account of people escaping, fire men putting out fire and protecting the equipment, we suggest the reasonable ventilation plan with different fire locations.