The tunnel width and the transverse fire’s position both impact the heat exhaust coefficient, which is a critical component of the lateral smoke exhaust in tunnel fires. In this research, the tunnel width and the transverse location of the fire source are varied to analyze the heat exhaust coefficient of lateral smoke exhaust. When tunnel width increases, there is a noticeable decrease in the longitudinal temperature of the entrained air and smoke layer in the fire plume. Furthermore, the heat exhaust coefficients are reduced. An increase in the distance between the exhaust vent and the fire source causes an increase in the proportion of hot smoke in the smoke exhaust mass flow, which increases the heat exhaust coefficient. A calculated heat exhaust coefficient was developed using the fire source’s location and the tunnel’s width as inputs, which agrees well with the simulation results. This method can predict the heat exhaust coefficient of the lateral smoke exhaust in tunnel fires. The findings of this study provide insight into how the tunnel width and the location of a transverse fire influence the heat exhaust coefficient.

The distribution characteristics of the temperature below ceilings in curved tunnel fires have not been quantitatively studied. A small-scale tunnel was constructed in this work to study the maximum temperature and longitudinal attenuation of the temperature below ceilings induced by fires in a curved tunnel with natural ventilation. Different tunnel turning radiuses and fire heat release rates were taken into account. The results show that the distribution characteristics of temperature below the tunnel ceiling is hardly affected by the tunnel turning radius in a scenario where the flame plume impinges on the ceiling (strong-plume-driven). The fire-induced maximum temperature and longitudinal attenuation of temperature in curved tunnels are comparable to those of straight tunnels. Improved correlations are proposed for the condition of a strong-plume-driven ceiling jet, and the measured value of the temperature of the experiment collapsed well. This work may enhance the understanding of temperature distributions in curved tunnel fires.

This study investigates the behavior of air supply in tunnels with multiple vertical shafts during fire incidents, focusing on natural ventilation dynamics. Numerical simulation is utilized to analyze the effect of different variables on air supply within vertical shafts. The findings reveal that the position of the smoke front significantly influences the direction and flow rate of gases during fire development. The mass flow rate of air supply during the stable fire development stage is influenced by the geometric size and positioning of vertical shafts, with shafts closer to the fire source exhibiting higher air flow rates. To address this issue, this study introduces a predictive model for estimating air flow rates in vertical shafts. This model exhibits a high level of accuracy when compared to simulations, offering a reliable method for predicting air flow rates based on the geometric characteristics of vertical shafts. Overall, this research contributes to understanding the complexities of air supply in tunnels with multiple vertical shafts, aiding in the improvement of natural ventilation strategies during fire incidents.

Due to the confined geometry of buildings, restricted smoke extraction leads to rapid accumulation and a sharp decline in visibility, severely impeding evacuation and rescue operations. Evacuation signage can help people quickly find the evacuation routes and achieve rapid evacuation in buildings. However, people’s recognition of the evacuation signage would be affected by the environmental visibility. But how the recognition time of evacuation signs changes under low visibility has not been studied in detail by any scholars yet. A experimental platform was developed to investigate the effects of smoke color, visibility, signage luminance, and flashing modes on recognition time under various smoke conditions. Analysis reveals that as visibility diminishes, the mean recognition time for dynamic evacuation signs increases significantly. At visibilities below 10 m, a luminance of 300 cd/m² is insufficient for rapid discernment of evacuation directions. However, under the low-visibility conditions in this study, when the luminance of the signage reaches a certain level, further increases in luminance did not significantly affect participants’ recognition time. The integration of the guidance strips significantly reduces mean recognition time and enhances accuracy as the strip luminance increases. Notably, under black smoke conditions, strip luminance exerts a more pronounced impact on recognition time. Furthermore, at a constant signage luminance, the flashing mode of guidance strips also effectively reduces recognition time. This study provides an experimental basis for optimizing the visual design and operating parameters of dynamic evacuation signage under low-visibility conditions, thereby supporting more effective evacuation guidance in fire emergencies.