Scholarly record
ASPECTS OF CRITICAL VELOCITY VARIATION FOR FIRE AND AIR POLLUTION CONTROL IN ROAD TUNNELS
Abstract
Fires in road tunnels pollute the ventilation air of the underground space and create unfavorable conditions for life. International recommendations for the design of emergency ventilation share the statement that the critical velocity (specifically its numerical value of 3.0 m/s) can be used to predict the spread of toxic substances in underground space and to exclude backflow for the majority of tunnels. Nowadays, it is advisable to supplement this point of view with the results of new studies, which notes that fires in underground conditions cause a dynamic pressure higher than the pressure created by tunnel fans. Based on CFD modelling, in presented paper we found that even at a critical velocity of 4.5 m/s in inclined tunnels with a heat release rate of 50 MW, jet fans can no longer influence on the ventilation flow, since their power is limited compared to the draft caused by fire. The current paper presents the results of the research, which distinguish the cases from each other: 1. when, based on the available classical knowledge, it will be possible to develop emergency ventilation projects to save lives, and 2. when the available knowledge is no longer sufficient to realize the mentioned projects and novel study results are needed to develop a new approach to the problem.
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References13
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