scholarly journals Numerical Simulations on the Extinguishing Effect of Water Mist System with Different Parameters of Longitudinal Ventilation in Curve Tunnel Fire

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Zhizhong Liu ◽  
Chen Chen ◽  
Mu Liu ◽  
Song Wang ◽  
Yuzhu Liu
Keyword(s):  
Operation Time ◽  
Water Mist ◽  
Wall Friction ◽  
Thermal Pressure ◽  
Smoke Flow ◽  
Effect Of Water ◽  
Tunnel Fire ◽  
Longitudinal Ventilation ◽  
Fire Extinguishing ◽  
Ventilation Velocity

Once a fire occurs in a long curve tunnel, the mixing of hot smoke flow and cold air leads to turbulence due to the curvature’s impact. This phenomenon results in a greater thermal pressure difference at the fire source and a substantially greater temperature field than in the straight tunnel. The longitudinal air flowing along the wall loses a lot of velocity in the curve tunnel due to the massive wall friction. Under the same fire extinguishing conditions, the curve tunnel and straight tunnel have different requirements for longitudinal ventilation. Factors such as tunnel curvature, longitudinal ventilation operation time, and ventilation velocity were all evaluated in order to investigate the influence of longitudinal ventilation parameters on the fire extinguishing effect of water mist in the curve tunnel. The fire extinguishing effect of water mist coupling with longitudinal ventilation in the curve tunnel is studied by numerical simulation, and the recommended values of ventilation operation time and ventilation velocity in the curve tunnel with the participation of the water mist system are given. The results show that (1) the fire extinguishing effect of water mist decreases with the increase of curvature under longitudinal ventilation and (2) fire prevention effect is best when water mist and longitudinal ventilation are used in the curved tunnel, and the ventilation velocity should be greater than 2 m/s.

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

2010 ◽  
Vol 168-170 ◽  
pp. 2473-2476 ◽  
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.

Simulation of smoke flow and longitudinal ventilation in tunnel fire

2006 ◽  
Vol 16 (3) ◽  
pp. 741-746 ◽  
Author(s):  
Gao-shang YANG ◽  
Yong-lin AN ◽  
Li-min PENG ◽  
Jin-hua ZHANG
Keyword(s):  
Smoke Flow ◽  
Tunnel Fire ◽  
Longitudinal Ventilation

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.

A Numerical Study Onfire Suppression of Water Mist in Microgravity

2014 ◽  
Vol 1016 ◽  
pp. 819-823
Author(s):  
Xue Han ◽  
Jun Qin ◽  
Jun Jun Tao ◽  
Ming Hui Feng
Keyword(s):  
Flow Rate ◽  
Numerical Study ◽  
Fire Suppression ◽  
Water Flow Rate ◽  
Simulation Method ◽  
Critical Value ◽  
Water Mist ◽  
Dominant Mechanism ◽  
Effect Of Water ◽  
Fire Extinguishing

Water mist technology has been developed and regarded as a promising substitute fire-extinguishing agent in spacecraft. In this paper, a numerical simulation method is introduced to investigate the effect of water mist size, velocity and flow rateon the fire suppressionefficiencyin microgravity. The fire extinguishing efficiency is better for the finer water mist in microgravity due to better heat transfer and more rapid vaporization. The evaporation cooling is the dominant mechanism of fire suppression in microgravity.As for the water mist velocity, the performance of fire suppression is affected slightly in microgravity. The results on the effect of water flow rate show that the flow rate should be higher than a critical value to suppress the fire effectively.

scholarly journals Effects of Discharge Area and Atomizing Gas Type in Full Cone Twin-Fluid Atomizer on Extinguishing Performance of Heptane Pool Fire under Two Heat Release Rate Conditions in an Enclosed Chamber

2021 ◽  
Vol 11 (7) ◽  
pp. 3247
Author(s):  
Dong Hwan Kim ◽  
Chi Young Lee ◽  
Chang Bo Oh
Keyword(s):  
Heat Release ◽  
Flow Rate ◽  
Heat Release Rate ◽  
Release Rate ◽  
Water Mist ◽  
Pool Fire ◽  
Sauter Mean Diameter ◽  
Discharge Area ◽  
Fire Extinguishing ◽  
Enclosed Chamber

In this study, the effects of discharge area and atomizing gas type in a twin-fluid atomizer on heptane pool fire-extinguishing performance were investigated under the heat release rate conditions of 1.17 and 5.23 kW in an enclosed chamber. Large and small full cone twin-fluid atomizers were prepared. Nitrogen and air were used as atomizing gases. With respect to the droplet size of water mist, as the water and air flow rates decreased and increased, respectively, the Sauter mean diameter (SMD) of the water mist decreased. The SMD of large and small atomizers were in the range of approximately 12–60 and 12–49 μm, respectively. With respect to the discharge area effect, the small atomizer exhibited a shorter extinguishing time, lower peak surface temperature, and higher minimum oxygen concentration than the large atomizer. Furthermore, it was observed that the effect of the discharge area on fire-extinguishing performance is dominant under certain flow rate conditions. With respect to the atomizing gas type effect, nitrogen and air appeared to exhibit nearly similar extinguishing times, peak surface temperatures, and minimum oxygen concentrations under most flow rate conditions. Based on the present and previous studies, it was revealed that the effect of atomizing gas type on fire-extinguishing performance is dependent on the relative positions of the discharged flow and fire source.

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