Evolution characteristics of fire smoke layer thickness in a mechanical ventilation tunnel with multiple point extraction

• Published in: Applied thermal engineering Vol. 111; pp. 248 - 256
• Main Authors: Mei, Fengzhu, Tang, Fei, Ling, Xiang, Yu, Jinshan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 25.01.2017
• Subjects: Ceiling extraction; Mechanical ventilation tunnel; Plug-holing; Smoke layer thickness; Tunnel fires; Tunnel fires; Mechanical ventilation tunnel; Smoke layer thickness; Ceiling extraction; Plug-holing
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2016.09.064

•Smoke layer thickness was studied in tunnel fires with multiple point extraction.•Smoke layer thickness was calculated by within-class variance method.•Plug-holing phenomenon was studied in tunnel fires with multiple point extraction. A series of burning experiments were conducted in a model-scale mechanical ventilation tunnel to study the characteristics of smoke layer thickness and plug-holing with multiple point extraction system. Hot-wire anemometer and thermocouples trees were used to measure the flow velocity of ventilation outlet and vertical temperature profile in a mechanical ventilation tunnel, respectively. It was found that the smoke layer thickness was calculated by integral ratio method and within-class variance method were good agreement with visual observation value. The normalized temperature curves can be divided into two regions, such as, the plug-holing and without plug-holing. The smoke plug-holing exhaust rate and the d/H ratio of smoke layer depth to clear height decreased with increasing the number of point extraction opening for a given HRR.