Studies Of The Genearation And Distribution Of CO In The Tunnel Model

Due to the special structure of the long tunnel space, when a fire occurs in the long tunnel, the generated toxic gas can not be eliminated in time, the internal temperature rises quickly, and as the ventilation in tunnel is relatively insufficient, the combustion becomes inadequate; CO, CO2and other toxic gas concentration will increase rapidly. In addition, because a lot of long tunnels are in the underground, the evacuation route is limited, once the fire ocuur, people will face great danger.In this paper, the major concern is how smoke transmiss to the remote place in the long tunnel, a large number of experimental and numerical simulation research carried out to reveal the CO generation and distribution in different fire conditions.In this thesis, experiments have firstly done in the two sizes of0.4m x0.8m x3.48m and0.6m×1.2m×>6m experimental models based on the application of Froude principles of similarity criterion, it found that carbon monoxide concentration in smaller size model is relatively higher than large size model, although in larger size model more fuel have been used.,and same to CO2, the calculated CO/CO2results show that in larger size model it is less than in smaller size models, so in smaller size model a greater proportion of carbon atoms are converted into carbon monoxide, the results show that carbon monoxide concentration does not comply with certain rules.When a slope tunnel gets fire, as the slope existence and fire smoke buoyancy is effected in sloping tunnels, temperature distribution, visibility, CO, CO2and O2concentration will change compared to the horizontal tunnel. Through the experiment in the tunnel slope which is found when the tilt angle is-10degrees, CO concentration will be much higher than other angles, and the smoke layer thickness and mass flow rate is lower than other angles, the discrepancy of smoke layer thickness and mass flow rate is not big in other anlges, and there exist slightly lower CO concentration compared to the horizontal tunnel model.it is also found that the smoke layer thickness will increase after fire extinguished.In order to study the vertical and horizontal distribution of CO concentration under longitudinal ventilation so as to reveal how smoke yields transmiss to the remote place, a series of experimental studie of CO concentration distribution have done in the tunnel model under longitudinal ventilation. It was found that when the speed of ventilation is less than0.94m/s, CO concentration stratification in remote place is more clear than near the fire place, and carbon monoxide is mainly concentrated in the higher region near the ceiling; when the speed bigger than0.94m/s, the smoke is turbulent flow, carbon monoxide concentration stratification cannot be seen. It is also found the maximum of carbon monoxide concentration decrease along the tunnel, and the maximum concentration has a delay time along along the tunnel.To study the effect of soot on CO generation, chemical numerical software Chemkin and one-dimensional premixed flame simulation has been applied. And different equilibrium rate of methane and O2are compared. The results showed that with the equilibrium rate increase, CO and CO2concentration will gradually increase, while CO increased vastly. When the soot is been considered, with the equilibrium rate increases, soot concentration increased significantly, and CO concentrations are lower when no consideration of the effect of soot. The concentration of OH decreased obviously when the soot is been considered, while the CO2and O2concentrations are slightly changed。...