Study On Fire Ventilation Mode Of Urban Fast Underground Tunnel

The number of motor vehicles in cities increased quickly in our country. It has exceeded the carrying capacity of the existing road traffic in the city. It is of great requirement to decrease the traffic pressure on the ground. Urban underground road not only can be quickly evacuated the cross-boundary traffic, to relief the road network pressure in central city, but also save travel time. However,the danger of tunnel fires are multiplied. Because of the narrow space, the smoke is difficult to control. The result may be very serious. So it is very important to study the underground road fire prevention.Numerical simulation and experimental method were used to study tunnel fire smoke exhaust mode in this thesis. In a series of tunnel fire tests, the temperature distributions and the spreading of smoke was measured. The results show that ventilation had a great influence on the temperature and the smoke distributions. N umerical simulations on tunnel fire in different modes of ventilation and smoke exhaust were carried out with FDS. The temperature, visibility and smoke distribution in the tunnel fire were analyzed in the ways of daily ventilation. The results show that daily ventilation cannot meet the requirement of tunnel fire ventilation and smoke exhaust. The effects of smoke exhaust velocity on the extraction effect were also analyzed. The exhaust volume of different fire scale was simulated. The results show that vent velocity has little effect on the smoke control effect. Exhaust volume has a great influence on the smoke control effect. The exhaust volume of 20 MW, 10 MW, 5MW heat release rate should not be less than 110m3/s, 100m3/s, 70m3/s respectively. The semi-transverse smoke extraction has a great influence on the smoke distribution. The critical wind velocity on different fire scale was studied, and the longitudinal ventilation mode was also analyzed. The results show that the critical wind velocity with fire at 5MW, 10 MW and 20 MW are 2m/s, 2.5m/s and 3m/s. The longitudinal ventilation can be used under normal traffic condition of fire. But it is not suitable for the condition of traffic block state. The semi-transverse smoke extraction system is more suitable for traffic jam condition.