scholarly journals Evaluation of Critical Velocity Employed to Prevent the Backlayering of Thermal Fume during Tunnel Fires.

2001 ◽  
Vol 67 (656) ◽  
pp. 911-918
Author(s):  
Qian WANG ◽  
Nobuyoshi KAWABATA ◽  
Takuji ISHIKAWA
Keyword(s):  
Critical Velocity ◽  
Tunnel Fires

Smoke Control in Subway Tunnel Fires

2014 ◽  
Vol 638-640 ◽  
pp. 2027-2030
Author(s):  
Xiao Xiong Zha ◽  
Sheng Zeng ◽  
Yi Yan Chen ◽  
Rui Juan Jiang
Keyword(s):  
Computer Simulation ◽  
Theoretical Analysis ◽  
Critical Velocity ◽  
Simple Formula ◽  
Control Mode ◽  
Subway Tunnel ◽  
Smoke Control ◽  
Release Rates ◽  
Tunnel Fires ◽  
Ventilation Velocity

This paper concerns the smoke control modes and the critical ventilation velocity when the subway tunnel on fires. The standard for the smoke control mode is making sure the smoke exhausting in the shortest way. The critical ventilation velocity means it is just sufficient to prevent the smoke spreading upstream. The critical velocity in different heat release rates obtained though theoretical analysis and computer simulation. In the end, a simple formula to calculate the critical velocity can be fitting out.

Effect of blockage ratio on critical velocity in tunnel fires

2012 ◽  
Vol 30 (5) ◽  
pp. 413-427 ◽  
Author(s):  
Liming Li ◽  
Xudong Cheng ◽  
Yu Cui ◽  
Sen Li ◽  
Heping Zhang
Keyword(s):  
Critical Velocity ◽  
Blockage Ratio ◽  
Tunnel Fires

Study of critical velocity and backlayering length in longitudinally ventilated tunnel fires

2010 ◽  
Vol 45 (6-8) ◽  
pp. 361-370 ◽  
Author(s):  
Ying Zhen Li ◽  
Bo Lei ◽  
Haukur Ingason
Keyword(s):  
Critical Velocity ◽  
Tunnel Fires

Numerical Simulation and Analysis of Critical Velocity in Tunnel Fires Based on FDS

2013 ◽  
Vol 831 ◽  
pp. 455-459
Author(s):  
Shu Hui Xu ◽  
Ling Fei Cui ◽  
Lei Ning ◽  
Zi Ye Wang
Keyword(s):  
Heat Release ◽  
Critical Velocity ◽  
Heat Release Rate ◽  
Release Rate ◽  
Small Scale ◽  
Smoke Control ◽  
Tunnel Fires ◽  
Tunnel Fire ◽  
Velocity Prediction ◽  
The One

Critical velocity is a very important parameter in smoke control of tunnel fires and the variation of critical velocity against fire heat release rate is also one of the most important issues in tunnel fire researches. In this paper, a simplified physical model of a tunnel was established and the predictions of critical velocity for fire sizes in the 5-100MW range were carried out by FDS simulations. The FDS-predicted dimensionless critical velocities were compared with the values calculated by Wu and Bakar’s model. The result indicated that when the heat release rate was relatively small, Q≤30MW, the critical velocity increased with the increasing of heat release rate and varied as the one-third power of the heat release rate; when Q≥40MW, the growth rate of critical velocity became very small; after Q reach to 60MW, the critical velocity was almost unchanged with the increasing of heat release rate. In addition, the values of critical velocity calculated by Wu and Bakar’model which was derived from small-scale gas fire tests were underestimated. Therefore, the model suggested by Wu and Bakar is not suitable for critical velocity prediction in tunnel fires.

scholarly journals Critical Velocity and Backlayering Conditions in Rail Tunnel Fires: State-of-the-Art Review

2019 ◽  
Vol 2019 ◽  
pp. 1-20
Author(s):  
Razieh Khaksari Haddad ◽  
Cristian Maluk ◽  
Eslam Reda ◽  
Zambri Harun
Keyword(s):  
Critical Velocity ◽  
State Of The Art ◽  
Experimental Testing ◽  
Public Investment ◽  
Flame Length ◽  
Theoretical Research ◽  
Tunnel Fires ◽  
Fire Source ◽  
Train Safety ◽  
Real Scale

The use of interurban and urban trains has become the preferred choice for millions of daily commuters around the world. Despite the huge public investment for train technology and mayor rail infrastructure (e.g., tunnels), train safety is still a subject of concern. The work described herein reviews the state of the art on research related to critical velocity and backlayering conditions in tunnel fires. The review on backlayering conditions includes the effect of blockages, inclination, and the location of the fire source. The review herein focuses on experimental and theoretical research, although it excludes research studies using numerical modeling. Many studies have used scaled tunnel structures for experimental testing; nevertheless, there are various scaling challenges associated with these studies. For example, very little work has been done on flame length, fire source location, and the effect of more than one blockage, and how results on scaled experiments represent the behaviour at real-scale. The review sheds light on the current hazards associated with fires in rail tunnels.

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