Definition and experimental evaluation of the smoke “confinement velocity” in tunnel fires |
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| Affiliation: | 1. Institute of Disaster Prevention Science and Safety Technology, Central South University, Changsha, Hunan 410075, China;2. State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026, China;3. Zhejiang Provincial Institute of Communications Planning, Design and Research, Hangzhou, Zhejiang 310006, China;1. College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai, 201306, PR China;2. State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui, 230026, PR China;1. Institute for Research in Construction, National Research Council, Ottawa, ON, Canada K1A 0R6;2. School of Mechanical Engineering, Southwest Jiaotong University, Chengdu, China;1. University of Tunis El-Manar, Faculty of Sciences of Tunis, Department of Physics, Laboratory of Energizing and Thermal and Mass Transfer, 2092, El-Manar, Tunis, Tunisia;2. University of Tunis El-Manar, Preparatory Institute for Engineering Studies El-Manar, 2092, El-Manar, Tunis, Tunisia |
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| Abstract: | An experimental study is carried out on a reduced scale tunnel model (scale reduction is 1:20). The main objective is to evaluate the longitudinal velocity induced into a tunnel when a fire plume continuously released is confined and extracted between two exhaust vents located on both sides of the fire source. For the experimental simulations, fire-induced smoke is simulated by an air and helium mix release. Smoke flow is symmetrical as regards the fire location and experiments are realized for an half tunnel with only one vent activated downstream the source. The vent extraction flow rate is step by step increased and the length of the stratified smoke layer downstream the vent as well as the longitudinal fresh air flow induced, are measured. A confinement velocity is then associated to the minimum value of the longitudinal air flow needed to prevent the smoke layer propagation downstream the vent. This velocity is evaluated for several values of the fire heat release rate and finally compared with the corresponding critical velocity obtained for a longitudinal ventilation system. |
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