Study on the critical velocity in a sloping tunnel fire under longitudinal ventilation

2016 ◽  
Vol 94 ◽  
pp. 422-434 ◽  
Author(s):  
Miao-cheng Weng ◽  
Xin-ling Lu ◽  
Fang Liu ◽  
Cheng-xian Du
Keyword(s):  
Critical Velocity ◽  
Tunnel Fire ◽  
Longitudinal Ventilation

scholarly journals Simulation Study on Critical Velocity of Longitudinal Ventilation Tunnel Fire

2013 ◽  
Vol 52 ◽  
pp. 67-71 ◽  
Author(s):  
Jun Deng ◽  
Li Ma ◽  
Zhen-ping Wang ◽  
Zhen Xing ◽  
Wei-feng Wang
Keyword(s):  
Critical Velocity ◽  
Simulation Study ◽  
Tunnel Fire ◽  
Longitudinal Ventilation

Effects of ambient pressure on the critical velocity and back-layering length in longitudinal ventilated tunnel fire

2019 ◽  
Vol 29 (7) ◽  
pp. 1017-1027
Author(s):  
Guanfeng Yan ◽  
Mingnian Wang ◽  
Li Yu ◽  
Yuan Tian
Keyword(s):  
Heat Release ◽  
High Altitude ◽  
Critical Velocity ◽  
Heat Release Rate ◽  
Release Rate ◽  
Ambient Pressure ◽  
Smoke Movement ◽  
Tunnel Fire ◽  
Longitudinal Ventilation ◽  
High Altitude Area

Nowadays, the critical velocity and back-layering length are the key parameters in longitudinal ventilation design. However, most studies research them at standard air pressure but ambient pressure decreases at high-altitude area and the reduced ambient pressure could affect the smoke movement characteristics in a tunnel fire. In order to investigate the effect of ambient pressure on the velocity and back-layering length in longitudinal ventilated tunnel, theoretical analysis was carried out first and a series of numerical simulation were conducted with varying heat release rate and ambient pressure. Results show that Li’s model is also reliable under various ambient pressures. The critical velocity under various ambient pressures would become larger with an increase in the heat release rate and would remain stable after the heat release rate reaches a certain value. At smaller heat release rate, the length of counterflow would be higher under reduced ambient pressure while it remains the same when the HRR is large. This could provide reference for tunnel ventilation design at high-altitude areas.

scholarly journals Review of Research on critical velocity in tunnel fire

2019 ◽  
Vol 79 ◽  
pp. 02001 ◽  
Author(s):  
Gui-hong Pei ◽  
Qiu-yi Zhang
Keyword(s):  
Influencing Factors ◽  
Critical Velocity ◽  
Release Rate ◽  
Fire Spread ◽  
Fire Control ◽  
Fire Source ◽  
Tunnel Fire ◽  
Longitudinal Ventilation ◽  
Tunnel Section ◽  
Ventilation Velocity

The critical velocity is the key for tunnel fire control. If the longitudinal ventilation velocity is greater than the critical velocity when the fire occurs, the upstream of the fire source is smokeless, and the smoke will flow to the downstream of the fire source, which can effectively control the fire spread and provide valuable time for personnel to escape and fire fighting. The researches of domestic and foreign scholars are used to investigate the influencing factors of critical velocity. the results show that the main influencing factors of critical velocity are fire heat release rate, tunnel section geometry, obstacle and slope in tunnel, etc. In this paper, the influencing factors are summarized, and some problems that need to be studied in tunnel fire are put forward.

COMPARISON BETWEEN LONGITUDINAL VENTILATION SYSTEM AND POINT EXTRACTION SYSTEM IN ROAD TUNNEL FIRE SAFETY

2021 ◽  
Vol 77 (1) ◽  
pp. 41-59
Author(s):  
Ti-Sheng HUANG ◽  
Nobuyoshi KAWABATA ◽  
Miho SEIKE ◽  
Masato HASEGAWA ◽  
Futoshi TANAKA ◽  
...  
Keyword(s):  
Fire Safety ◽  
Ventilation System ◽  
Extraction System ◽  
Road Tunnel ◽  
Tunnel Fire ◽  
Longitudinal Ventilation

The Study of the Confinement Velocity in the Longitudinal Ventilation Tunnel Fire

2012 ◽  
Vol 446-449 ◽  
pp. 3665-3669
Author(s):  
Ke Qing Sun ◽  
Hui Yang
Keyword(s):  
Characteristic Parameter ◽  
Experimental Models ◽  
Experimental Results ◽  
Mixed Gas ◽  
Control Effect ◽  
Smoke Control ◽  
Tunnel Fire ◽  
Longitudinal Ventilation ◽  
The Relationship ◽  
Two Sides

For the situation that the smoke exhaust vents are located on both sides of the fire source, critical ventilation velocity is not appropriate to evaluate the smoke control effect. “Confinement velocity” is proposed as the characteristic parameter to study the longitudinal ventilation by O.Vauquelin in this situation. However, there have been few studies on confinement velocity. An experimental study was carried out on two reduced scale tunnel models. The main objective is to analysis the relationship between confinement velocity and fire heat release in this situation. Helium and air in different ratio was used as the smoke, and the "cold smoke" produced by smoke generator was put into the mixed gas in order to measure the length of smoke layer. The experimental models were based on the half tunnel as flow field at two sides of fire is symmetrical. The CFD model was created on the basis of the experiment, and the results were basically accord with the experimental results. It was shown from the experimental results that the critical point of the confinement velocity is between L / H = 2 to L / H = 4 in section 1, between L / H = 1 to L / H = 2 in section 2, rather than a fixed value; Two tunnel models had similar dimensionless confinement velocity, but the dimensionless total confinement velocity was different.

Sign in / Sign up

Export Citation Format

Share Document