Paper 3: Volume 5 No.2 Sept 2006 Edition
CFD-Aided
Tenability Assessment of Railway Tunnel Train Fire Scenarios
Yunlong
Liu*, Xijuan Liu and Bradley Paroz
Fire Science
and Technology Laboratory, CSIRO Manufacturing and Infrastructure
Technology,
PO Box 310 North
Ryde, NSW 1670,
Australia
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Abstract
Five fire
scenarios have been simulated with the CFD model Fire Dynamics Simulator (FDS)
to analyse the performance-based fire safety design of a 2935 m-long
railway tunnel. The influence of tunnel longitudinal ventilation fan
activation time, fire size and the type of burning materials on tunnel
tenability was investigated based on variations of two primary scenarios:
Scenario #1 assumed a 15 MW fire at the front end of a train, and
Scenario #2 assumed a 15 MW fire at the rear of a train. In both
scenarios the burning material was assumed to be predominantly
polyurethane, and tunnel fans were assumed to activate 901 seconds
after fire initiation. Scenario #3 was a variation of Scenario #1 with the
dominant burning material changed to wood; Scenario #4 was a variation of
Scenario #2 which assumed that fans activated 180 seconds after fire
initiation; and Scenario #5 was a 6 MW fire, which was scaled down
from the 15 MW fire of Scenario #1.
For all of the scenarios,
a reversible bi-directional ventilation strategy was implemented, and the
worst wind condition was considered. The burning materials (polyurethane
and wood) were assumed to generate a soot rate of 10% and 1% per unit
weight of fuel respectively. Maximum tenable time (known as Available Safe
Egress Time, ASET hereafter) was computed based on a visibility limit of
10 m at a height of 2.1 m.
CFD virtual realisation
results showed that the fire heat release rate, type of dominant burning
material and the activation time of Smoke Management Systems (SMS) fans
all influence tenability times within the tunnel. It is suggested that all
these factors must be considered in the performance-based fire safety
design and the accident management of a tunnel.
Key words: railway,
train fire, tunnel ventilation, CFD, smoke management.
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