Numerical Simulation Study On Spiral Highway Tunnel Fire

With the increasingly maturing tunnel design theory and the improvement of tunnel construction technology level, the linear design of modern highway tunnel is no longer exactly the same with the older concept that keeping a straight tunnel line shape rather than a bend one. Now designers break this idea, more and more spiral curve highway tunnels appear in front of the world with their advantages such as can overcome the elevation difference, avoid the bad geological. The law of the spread of fire smoke in the curve tunnel must be different from the same law in the general straight tunnel because of the influence of its curvature, slope and other factors. Therefore, to carry out the spiral curve highway tunnel fire research is of great significance. This thesis depends on the reduced scale experiment model of the spiral curve highway tunnel in Sichuan fire research institute, apply CFD simulation technology, and study on the spread characteristics of the spiral curve highway tunnel fire smoke, the ventilation and the smoke exhaust.At first, this paper summarizes the development of the highway tunnel in the recent years, highway tunnel fire and its harm, and the current research status at home and abroad of highway tunnel fire is analyzed. Then, the paper introduces the computational fluid dynamics theory and fire turbulent numerical simulation theory, based on these theory knowledge, use the software CFX to establish the reduced scale numerical model of spiral curve tunnel, calculate the spiral curve tunnel fire and the simulation results are compared with the test results to analyze and verify the feasibility of numerical analysis method. Finally, the full scale numerical simulation research of the spiral curve highway tunnel fire is carried out. The main contents and results are as follows:(1) Based on the basic theory of computational fluid dynamics, heat transfer, combustion and highway tunnel ventilation, the full scale calculation model of the spiral curve highway tunnel was established by CFX, and its boundary conditions were determined. According to Guidelines for Design of Ventilation of Highway Tunnel and the research results at home and abroad, determine the spiral curve highway tunnel fire scale and calculated conditions.(2) By changing the curvature, fire source position and fire scale, analyzes the law of the distribution of temperature field, visibility and velocity field in the tunnel, obtain the influence of the three kinds of factors on the spiral curve highway tunnel fire smoke spread characteristic, provide relevant reference to the other curve tunnel fire prevention design engineering.(3) According to the simulation results of the spiral curve tunnel fire under the action of different longitudinal wind speed, explore the validity of the jetting longitudinal smoke extraction mode in the spiral curve tunnel under the conditions: without the natural wind, with the positive natural wind and with reverse natural wind, and the natural wind speed which is outside of the tunnel and allowed to exist were given. By analyzing the efficiency of the smoke extraction mode which using the ventilation shaft under the action of different speed of induced airflow, the validity of this mode and the corresponding reliable value of induced airflow were obtained.