Computational analysis on longitudinal ventilation in tunnel fire

Pao Yue-kong Library Electronic Theses Database

Computational analysis on longitudinal ventilation in tunnel fire

 

Author: Lau, Chi-hung
Title: Computational analysis on longitudinal ventilation in tunnel fire
Degree: M.Sc.
Year: 2003
Subject: Hong Kong Polytechnic University -- Dissertations
Tunnels -- Ventilation
Tunnels -- Fires and fire prevention
Department: Dept. of Building Services Engineering
Pages: ii, 59, [63] leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1733106
URI: http://theses.lib.polyu.edu.hk/handle/200/829
Abstract: Rapid growth of population in major cities around the world , brings problems on transportation. Underground transit systems are provided for mass transportation. However, public awareness of fire safety inside tunnels is relatively weak. In case of a fire, occurs in the tunnel, consequences would be very serious. Smoke and combustion toxic gases generated from a fire will spread along the tunnel rapidly. Smoke control in a tunnel fire is a major concern in designing tunnel ventilation systems. To provide a smoke free path for evacuation in emergency. longitudinal ventilation scheme has been widely adopted. This topic will be studied in the thesis. Previous studies quantified the critical velocity, minimun annular air velocity applied to prevent backlayering, will be reviewed. Since smoke spreading inside tunnel is a three-dimensional turbulent phenomena, there are very little experimental evidence to support their validity to evaluate critical velocity with various tunnel geometries. On the other hand, future development of railway will be introduced more complexity tunnel network and geometry. The critical velocity is a key parameter to evaluate the performance of longitudinal ventilation system. Several approaches based on experimental results, application of zone model had been proposed. A comprehensive review on previous studies on critical velocity and the full-scale test performed under Memorial Tunnel Fire Ventilation Test Program (MTFVTP) [10] was performed. Further to different analytic approaches, computation fluid dynamics (CFD) approach was also applied to study the tunnel smoke spreading under forced ventilation. CFD approach to critical velocity was investigated. With the aid the rapid technology development during the past decay, the application of computer models in the design was facilitated. The use of CFD can allow the designers to check whether or not the design operation condition of tunnel ventilation equipment is high enough or not to prevent backlayering.

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