W. Tang, L. H. Hu and L. F. Chen (2013) Effect of blockage-fire distance on buoyancy driven back-layering length and critical velocity in a tunnel: An experimental investigation and global correlations. Journal/Applied Thermal Engineering 60 7-14. [In English]
Web link: http://dx.doi.org/10.1016/j.applthermaleng.2013.06.033
Keywords: Tunnel fire, Back-layering length, Critical velocity, Vehicular, blockage-fire distance, Longitudinal ventilation, CRITICAL VENTILATION VELOCITY, ROAD TUNNEL, WIND-TUNNEL, SMOKE FLOW, POOL FIRES, AIR-FLOW, TEMPERATURE, BEHAVIOR, GASOLINE, GAS
Abstract: Experiments are conducted in a model tunnel to study the effect of a vehicular blockage at the upstream of the fire source on the buoyancy driven back-layering length and critical velocity in a longitudinal ventilated tunnel. The relative distance between the vehicular blockage and fire source are ranged in 1 m similar to 6 m. It is found that with no blockage, experimental data on back-layering length and critical velocity can be well collapsed by Wu model and Li model, respectively. However, with the increase in blockage-fire distance, both the back-layering length and critical velocity first decrease then approach to constants similar to those with no blockage. The modified Wu model and Li model amended by cross-sectional blockage ratio proposed by Lee, which does not include the factor of blockage-fire distance, still fail to predict experimental results for different blockage-fire distances. Thus a dimensionless modification coefficient eta is proposed and correlated non-dimensionally with the normalized blockagefire distance to account for this effect. Finally, global models are proposed to predict back-layering length and critical velocity including factors of both cross-sectional blockage ratio and blockage-fire distance, which are shown to well collapse the experimental measurements in good agreement. (C) 2013 Elsevier Ltd. All rights reserved.