A study on smoke control system in a fully-transverse ventilated tunnel

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A study on smoke control system in a fully-transverse ventilated tunnel


Author: Yang, Diyao
Title: A study on smoke control system in a fully-transverse ventilated tunnel
Degree: M.Sc.
Year: 2012
Subject: Smoke prevention.
Tunnels -- Fires and fire prevention.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: xi, 119 leaves : ill. ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2551465
URI: http://theses.lib.polyu.edu.hk/handle/200/6919
Abstract: In recent years, road tunnels become more and more popular in our daily life. Fire safety is one of the major concerns in these road tunnels. Fire accidents in road tunnels not only result in injuries or fatalities of people, damage or loss of properties, but also lead to public concerns on using such transportation facilities. A better understanding of tunnel fire and smoke phenomenon is important to the fire engineers and authorities as more information will help to create a safer tunnel environment. Tunnel smoke control systems, which include longitudinal, semi-transverse and fully-transverse systems, are usually employed to control the fire development and smoke propagation at fire emergencies. As fully-transverse ventilation systems are widely applied in long tunnels and tunnels with large cross section areas recently, the present study is to investigate the smoke and fire control performance of fully-transverse ventilation system. In this study, a review of legislation aspects on the design of tunnel smoke control system has been presented and previous studies on the tunnel fire have been reexamined. The smoke and fire control performances of fully-transverse ventilation system, together with the natural and semi-transverse ventilation systems, have been investigated both experimentally and numerically.
Small-scale tunnel fire experiments have been conducted with three different ventilation strategies - natural, semi-transverse and fully-transverse systems. The spatial temperature profiles and smoke propagation patterns have been recorded. The obtained data have been analyzed and compared case by case. It has been found that the semi-transverse and fully-transverse ventilation systems play important roles on the smoke control and heat removal. The transversely ventilated systems have better smoke and fire control abilities when compared with natural ventilation system. In the transversely ventilated systems, thinner smoke layers and lower temperature profiles are achieved. For the design of fully-transverse ventilation systems, it has been found that the ratio of supply air rate and exhaust air rate (Vs/Ve) is an important parameter in both smoke and temperature control. It is suggested that a Vs/Ve under 40% is suitable to maintain a smoke layer and to remove heat. Longitudinal air flow is created by zoned operation strategy, it is observed that the zoned operation in fully-transverse ventilation system has a similar working principle as longitudinal ventilation system. To validate against the experimental data and give more in-depth analysis on the fire and smoke phenomenon, Computational Fluid Dynamics (CFD) techniques were utilized. In general, Fire Dynamics Simulator (FDS) version 5.5.3 is able to capture the trend of fire development and the predicted temperature profiles are reasonably well-matched with the experiment. However, differences have been found mainly because simplification assumptions are made in the numerical models.

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