scholarly journals Critical velocity for preventing thermal backlayering flow in tunnel fire using longitudinal ventilation system: Effect of floor-fire separation distance

2022 ◽  
Vol 171 ◽  
pp. 107192
Author(s):  
Soufien Gannouni
Keyword(s):  
Critical Velocity ◽  
Ventilation System ◽  
Separation Distance ◽  
System Effect ◽  
Tunnel Fire ◽  
Longitudinal Ventilation

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

scholarly journals Numerical 3D Simulation of a Longitudinal Ventilation System: Memorial Tunnel Case

2006 ◽  
Author(s):  
Monica Galdo-Vega ◽  
Rafael Ballesteros-Tajadura ◽  
Carlos Santolaria-Morros
Keyword(s):  
Numerical Models ◽  
Ventilation System ◽  
Fire Behavior ◽  
Full Scale ◽  
3D Simulation ◽  
Full Scale Test ◽  
Road Tunnel ◽  
Tunnel Fire ◽  
Longitudinal Ventilation ◽  
Scale Test

In this work, a numerical 3D simulation of a longitudinal ventilation system is developed to analyze the fire behavior inside a road tunnel. Recent disasters, like crashes in the Mont Blanc tunnel (France, 1999) or San Gottardo (Italy, 2001), have shown the need for better integral actions during possible fire incidents. The minimum delay time, required for starting the jet fans, or the evolution of the smoke patterns inside the tunnel are critical issues when rescue plans are designed. Some methods to study the smoke propagation during a fire are: pseudo-thermal scale models, full scale test and numerical models. Several contributions using the first method can be found in references [1], [2] and [3]. However it is very difficult to extrapolate the results from this kind of models. The second method (full scale test) is the most expensive of all and only two of them have been conducted recently: EUREKA Project [4] and the Memorial Tunnel Fire Ventilation Test Program [5]. The last method (numerical models) it is now under development. The objective of this work is to validate a numerical model, to predict the behavior of the smoke generated during a fire incident inside a road tunnel, comparing its results with previous experimental data collected in the Memorial Tunnel Project. In addition, a good agreement was achieved, so a methodology to predict the performance of a longitudinal ventilation system in case of fire was accurately established.

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 Numerical Simulation of Critical Velocity in Ventilation

2016 ◽  
Vol 11 (2) ◽  
pp. 19
Author(s):  
Jabar Kesadian ◽  
Armen Adamian
Keyword(s):  
Critical Velocity ◽  
Longitudinal Velocity ◽  
Ventilation System ◽  
Longitudinal Ventilation ◽  
Ventilation Shaft ◽  
Safety And Health ◽  
Velocity Flow ◽  
Before And After ◽  
Fluent Software ◽  
Effect Parameter

Given the importance of the safety and health of passenger’s in underground tunnels, analysis and simulation of fires in tunnels is to design a ventilation system. Longitudinal ventilation systems are widely used in tunnel ventilation and are one of the most important parameters for fire safety in this type of critical velocity system. Critical velocity of ventilation is minimum longitudinal velocity flow of air that prevents the smoke from the fire to the upstream flow.In this study, the effects of the distance between the fire source of the tunnel, obstacle before and after the fire, several sources of fire in the tunnel and ventilation shaft tunnels will be discussed on the critical velocity. Each effect parameter according to a correlation analysis of numerical results obtained using the solver FLUENT software Airpak and then the relationship between dimensionless critical velocity and dimensionless heat release are stated.

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.

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

Experimental study of back-layering length and critical velocity in longitudinally ventilated tunnel fire with various rectangular cross-sections

2021 ◽  
pp. 103483
Author(s):  
Tianhang Zhang ◽  
Ganyu Wang ◽  
Jiangdong Li ◽  
Yadong Huang ◽  
Kai Zhu ◽  
...  
Keyword(s):  
Experimental Study ◽  
Critical Velocity ◽  
Cross Sections ◽  
Tunnel Fire

A New Advance in Tunnel Ventilation Design Planning

2017 ◽  
Author(s):  
Mark P. Colino ◽  
Elena B. Rosenstein
Keyword(s):  
Ventilation System ◽  
National Fire Protection Association ◽  
Capital Cost ◽  
Smooth Transition ◽  
Mechanical Equipment ◽  
Tunnel Ventilation ◽  
Tunnel Fire ◽  
Ventilation Shaft ◽  
Emergency Ventilation ◽  
Ventilation Fan

The new train signaling, traction power and tunnel ventilation system coordination guidelines enacted in National Fire Protection Association (NFPA) Standard 130 have brought the necessity and cost of tunnel ventilation fan shafts into greater focus. The guidelines were aimed at coordinating the three aforementioned rail systems to control the number of trains that could be between successive ventilation shafts during an emergency — in recognition of the fact that the best protection to both incident and non-incident train passengers and crew is to allow no more than one train in each ventilation zone. Though based in safety, these new NFPA guidelines can substantially expand the capital cost and environmental impact of new rail tunnel projects by adding more ventilation shafts and tunnel fan equipment to the scope of work. In addition, the resulting increase in the required number of ventilation shafts and tunnel fan equipment can hinder existing railroad properties as they seek to either increase their train throughput rates, or reduce their tunnel electrical infrastructure. Fortunately, a new kind of emergency ventilation shaft has been developed to facilitate compliance with the NFPA 130 Standard without the excessive capital cost and far-reaching environmental impacts of a traditional emergency ventilation shaft. This new kind of emergency ventilation shaft is called the Crossflue. The Crossflue is a horizontal passage between parallel rail tunnels with a single ventilation fan-motor unit installation. The Crossflue fan is designed to transfer air/smoke flows from one (occupied, incident) tunnel to another (unoccupied, non-incident) tunnel — thereby protecting the incident tunnel at the expense of the non-incident tunnel. The Crossflue passage has angled construction to allow a smooth transition of airflows both into and out of the adjoining tunnels. In addition to the fan, the Crossflue contains a ventilation damper, sound attenuators, ductwork transitions and flexible connectors within the fan equipment line-up; the functionality of all this mechanical equipment is described in the paper. To preserve underground space and minimize the rock excavation, the Crossflue fan is both remotely-powered and remotely-controlled; the fan is only operated as part of a pre-programmed response to tunnel fire events. The methodology utilized to design the Crossflue was taken from the Subway Environmental Design Handbook (SEDH); the SEDH [1] was specifically developed for rail tunnel ventilation design and is the preeminent reference volume in the industry. In summary, the Crossflue provides a dual benefit of achieving NFPA 130 compliance, while at the same time minimizing the construction, equipment, environmental, and energy costs of a traditional tunnel ventilation shaft.

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