Effects of fire-blockage distance on pool fire burning behavior and thermal temperature profiles in a naturally ventilated tunnel

Previously, investigation of blockage effect on the fire burning behavior and thermal characteristic was mostly conducted in longitudinally ventilated tunnels. This paper predominately concentrated on the pool fire burned in a naturally ventilated tunnel considering blockage effect caused by the vehicle and wall restriction due to the closed portal. A total number of 45 reduced scale experiments were carried out in a 1/15 model tunnel where pool fires loaded in five fuel pans were burned with and without blockage. Two blockages were individually placed upstream of the fire at five locations to investigate the impact of fire-blockage distance L-fb and blockage ratio. Results declared the key findings as: 1) blockage nearby the pool fire results in asymmetric entrainment of fire plume, due to which flame of the pool fire swings severely during the combustion; 2) burning rate of the pool fire significantly increases when the fire-blockage distance L-fb decreases, attributed to the enhanced heat feedback from the blockage. For the two blockages adopted in the present work, burning rate increases as blockage ratio increases; 3) ceiling temperature decreases as the fire-blockage distance L-fb increases. An empirical model was established to correlate ceiling temperature decay upstream of the fire with fire-blockage distance L-fb. Comparison between the predicted model and experimental values indicates good agreement.