Smoke Exhaust Rate and Exhaust Vent Distribution of the Point Exhaust System in Tunnel Fire

The smoke exhaust rate and the arrangement of the exhaust vents are the key factors that can affect the smoke control effect in tunnel fire. The smoke production rate with different heat release rates and different tunnel widths was studied by a numerical method. The effects of different smoke exhaust rates and the distribution of the exhaust vents on the smoke spreading length and the heat exhaust efficiency were also investigated. Results show that the smoke production rate is closely related to the heat release rate of the fire source, the width of the tunnel and the length of smoke spread. It is difficult to control the smoke within the length of 300 m which is suggested in the "Guidelines for Design of Ventilation of Highway Tunnels" using the recommended smoke exhaust rate in the relative tunnel design codes. If the design objective is to control the smoke in a certain range, there is a linear relationship between the control range of smoke and the opening range of the exhaust vent, and the distribution of the exhaust vent can be optimized following the relationships.