Research on the phenomenon of plug-holing under mechanical smoke exhaust in tunnel fire

When a fire occurs in a tunnel, smoke control is very important for people's safety. Extraction systems were designed in order to extract smoke in tunnel. In this study, Fire Dynamics Simulator (FDS) was used to research the plug-holing on tunnel tire for it will significantly reduce the efficiency when it occurs. A series of mechanical exhaust velocity with different heat release rate were simulated, the plug-holing issue on a heat release rate was determined by N-percentage rule. N = 20 in our study is based on previous studies and our experimental research. We analysis the critical exhaust rate determined by N-percentage rule on different heat release rate, and find that the critical Froude number 1.5 used to determine the onset of plug-holing in enclosed buildings can't be used in tunnel tire. However, a critical Froude number 2.1 could be used in determining the onset of plug-holing in tunnel fire. (C) 2013 International Association for Fire Safety Science. Published by Elsevier Ltd. Open access under CC BY-NC-ND license.