Smoke Management in Tunnels with Longitudinal Ventilation System: An Experimental and Numerical Study

The ventilation system in tunnels serves dual roles, providing fresh air for comfort in normal conditions and managing smoke during emergencies. It maintains air quality for a safe environment in routine operations, safeguarding occupants. In emergencies, it crucially aids in smoke control, ensuring safety for rescue efforts and limiting fire spread. Regular tests are essential to validate safety systems, a prerequisite for tunnel usage approval. These tests typically involve fire and smoke assessments, verifying control and evacuation systems. Compliance ensures system efficacy, public safety, and risk mitigation through continuous improvement, enhancing overall tunnel safety and reliability. The current study experimentally analyzed the performance and behavior of the longitudinal ventilation system and related sub-systems in hot smoke control and toxic gas management through a standard fire test. Based on the test results and experimental data, a suitable numerical simulation model was developed to predict the behavior of the ventilation system in larger fires as well. The numerical and experimental results of this study indicate that a properly functioning ventilation system can lead to the creation of a safe and smoke-free environment on both sides of a fire. This effect is more noticeable in small fires where the fire's heat release rate is low and the tunnel cross-section is relatively large. In such scenarios, smoke tends to gather at higher levels during the initial stages of the fire, with only a small amount descending to lower levels. However, in cases of high-intensity fires, the situation changes significantly, and smoke settles, particularly downstream, on the tunnel floor after a certain period of time. The presence or absence of traffic was also observed to affect the quality of smoke dispersion and propagation. Additionally, the findings of this study can assist emergency fire response teams in managing safety within tunnels under diverse circumstances.