Experimental and numerical studies on the smoke extraction strategies by longitudinal ventilation with shafts during tunnel fire

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.

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

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2006-98259 ◽

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.

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Tunnel Fire Dynamics as a Function of Longitudinal Ventilation Air Oxygen Content

Sustainability ◽

10.3390/su11010203 ◽

2019 ◽

Vol 11 (1) ◽

pp. 203 ◽

Cited By ~ 7

Author(s):

Sanjay Kumar Khattri ◽

Torgrim Log ◽

Arjen Kraaijeveld

Keyword(s):

Oxygen Content ◽

Oxygen Concentration ◽

Ambient Air ◽

Fire Dynamics ◽

Maximum Heat ◽

Tunnel Fire ◽

Longitudinal Ventilation ◽

Rate Maximum ◽

Air Ventilation ◽

Safety Parameters

Longitudinal ambient air ventilation is the most common methodology for maintaining an amicable environment in tunnels during normal operations while providing an evacuation path during tunnel fire emergencies. The present work investigates the influence of forced ventilation air oxygen concentrations on tunnel fire dynamics. Mixing inert gasses such as nitrogen, argon, or carbon dioxide with ambient air changes the ventilation air oxygen concentration. In order to quantify the influence of the oxygen content on the critical tunnel safety parameters, multiple computational fluid dynamics (CFD) simulations were done on a reduced-size tunnel while preserving the system Froude number. Analytical expressions were developed to describe the importance of oxygen content on the tunnel fire dynamics. By employing Froude scaling, the resulting relations were extrapolated to real scale tunnels. For the ambient air ventilation, the extrapolated expressions displayed good agreement with experimental literature data. By adjusting the oxygen concentration, parameters such as maximum tunnel ceiling temperature, fire growth rate, maximum heat flux to the tunnel floor, maximum flux on the tunnel ceiling, and maximum heat release rate can be controlled. This is the case also for oxygen levels where people can survive. This may increase the possibility for evacuation and improve the conditions for firefighting, significantly improving tunnel fire safety.

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Experimental investigation of the thermal back-layering length in a branched tunnel fire under longitudinal ventilation

International Journal of Thermal Sciences ◽

10.1016/j.ijthermalsci.2021.107415 ◽

2022 ◽

Vol 173 ◽

pp. 107415

Author(s):

Youbo Huang ◽

Yanfeng Li ◽

Jiaxin Li ◽

Ke Wu ◽

Haihang Li ◽

...

Keyword(s):

Experimental Investigation ◽

Tunnel Fire ◽

Longitudinal Ventilation

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Reduced-Scale Model Tests of Fires in Railway Tunnel and Structure Fire Safety

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.2473 ◽

2010 ◽

Vol 168-170 ◽

pp. 2473-2476 ◽

Cited By ~ 1

Author(s):

Hong Li Zhao ◽

Zhi Sheng Xu ◽

Xue Peng Jiang

Keyword(s):

Fire Safety ◽

Numerical Models ◽

Scale Model ◽

Railway Tunnel ◽

Tunnel Fires ◽

Tunnel Fire ◽

Longitudinal Ventilation ◽

Overall Stability ◽

Reduced Scale ◽

Ventilation Velocity

The high-temperature toxic gas released by long railway tunnel fires not only causes great harm to persons, but also damages the structure of the tunnel which will reduce the overall stability of tunnel. In order to diminish the damage to tunnel structure produced by a tunnel fire, on the basis of the first extra-long underwater railway tunnel in China, some reduced-scale tests were carried out to study the distribution of smoke temperature along the tunnel ceiling, the smoke velocity and the backlayering distance with the fire size of 63KW. The longitudinal ventilation velocity and the tunnel gradient varied in these tests. The smoke temperature below the tunnel ceiling in different times and under different longitudinal ventilation velocity, the smoke velocity under the ceiling, and the backlayering distance in the presence of different ventilation velocity are acquired from the tests. The conclusions have the guiding meaning to the disaster prevention design and construction of structure fire safety in tunnel fires, and all the experimental data presented in this paper are applicable for the verification of numerical models.

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