Study on hybrid ventilation modes for urban tunnel fires

Aimed at the problem of not being able to fully guarantee safe evacuation in case of urban tunnel fires with semi-open natural ventilation, the Fire Dynamic Simulation (FDS) software and a wind tunnel experimental platform were used to carry out a numerical simulation and experimental study on how smoke diffuses under natural ventilation and hybrid ventilation modes. The results show that natural ventilation used in a semi-open urban tunnel is unable to solve the problems of fire safety, but hybrid ventilation can effectively control smoke when the exhaust coefficient reaches 3.3, which assures the safe evacuation of personnel and vehicles. Additionally, the exhaust coefficient presented in this paper and applied in the study of the hybrid ventilation mode for semi-open urban tunnels may provide a theoretical basis for similar tunnels regarding safety during fires.