Control of ventilation airflow for tunnel fire safety

Behavior of fire-induced heat and smoke movement in a longitudinally ventilated model tunnel is studied experimentally. A gas burner is used as fire source. Ventilation velocity, heat release rate, temperature distributions an measured under quasi-steady conditions. Flow visualization using incense smoke as a tracer has been carried out to identify some important characteristics of the flow and heat transfer, such as the upstream layer, thermal stratification, turbulence mixing, etc. Flow patterns under different ventilation velocities are analyzed and discussed. It is found that heat and smoke can be controlled by proper ventilation. Optimum environment for initial evacuation and fire services should be provided at a ventilation velocity close to or slightly less than the critical ventilation velocity, which is a function of the cube root of the heat release rate. The effects of heat release rates and tunnel inclination angles were also investigated.