Influence of upstream blockage on smoke control in tunnel fires
Ying Zhen Li, Haukur Ingason
Abstract
Smoke control in a longitudinally ventilated tunnel with various blockage conditions was investigated experimentally. A total of 28 tests were conducted with a focus on single blockage with a short distance from the fire source, continuous blockage and semicontinuous blockage. Both gas and pool fires were used. The aim was to understand the influence of blockage on critical velocity and babcklayering length. The results confirm that blockage ratio is a critical parameter when determining the critical velocity and backlayering length. The longitudinal location of the blockage in relation to the fire source also influences the values of critical velocity and backlayering length. The experiments presented are in scale 1 to 3.3 and represents a medium sized tunnel. The focus was on free flow conditions and blockage ratios of regular sizes. For the various tested scenarios with single blockage, the reduction ratio of critical velocity appears to be slightly less than the blockage ratio. However, when the blockage is attached to the upstream side of the fire source, the reduction ratio of critical velocity approximately equals the blockage ratio.