Full-scale experimental investigation on smoke spreading and thermal characteristic in a transversely ventilated urban traffic link tunnel

Transverse ventilation system is an effective method to control the smoke propagation in tunnel fires. In the current research, 14 full-scale burning tests were conducted in an urban traffic link tunnel in Chongqing, China. Temperature and velocity profiles, as well as the smoke stratification characteristics affected by the transverse ventilation were successively explored. Results underlined that 1) Fire location and air supply system have limited influence on the induced air velocity while the induced air velocity slightly decreased as heat release rate increased. When more smoke outlets were activated, the induced air velocity increased; 2) Ceiling temperature was very sensitive to the fire location, smoke extraction, and air supply system. A distinct temperature decrease was observed when (a) the fire moved closer to the outlet; (b) more outlets were activated; (c) supply vents near the fire were opened; 3) Thermal stratification could be well predicted by the temperature quotient proposed by Newman. Considering the transverse ventilation, the relationship between temperature ratio Delta T-cf/Delta T-avg and Froude number F-r accounting for the transverse ventilation was modified based on the present measurements.

Automated summary

The study highlights the significant impact of transverse ventilation on smoke propagation in tunnel fires. Factors such as fire location, air supply system, and heat release rate influence the speed of smoke spread. Activating more smoke outlets can increase the induced air velocity, facilitating quicker smoke extraction.