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Journal articles on the topic 'Backlayering'

Author: Grafiati

Published: 4 June 2021

Last updated: 4 May 2024

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1

Leong, Jik Chang, C. L. Chang, Y. C. Chen, and L. W. Chen. "Smoke Propagation in an Inclined Semi-Circular Long Tunnel." Advanced Materials Research 446-449 (January 2012): 2143–48. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.2143.

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This work used FDS to simulate tunnel fires occur in a semi-circular longitudinally ventilated tunnel. By varying the parameters such as the tunnel gradient, the fire size, and the ventilation velocity, their influence on the backlayering effect and downstream propagation rate can be recognized. Under weak ventilation, the backlayering effect either advances or vanishes depending on the slope of the tunnel. Under stronger ventilation, the backlayering effect would break up. The temperature distributions may become less and less dependent on the tunnel gradient when the ventilation velocity is increased. Although the hot gases and smoke in uphill tunnels propagate faster than those in downhill tunnels, their difference reduces with ventilation velocity.

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2

Ho, Yu-Tsung, Nobuyoshi Kawabata, Miho Seike, Masato Hasegawa, Shen-Wen Chien, and Tzu-Sheng Shen. "Scale Model Experiments and Simulations to Investigate the Effect of Vehicular Blockage on Backlayering Length in Tunnel Fire." Buildings 12, no. 7 (July 13, 2022): 1006. http://dx.doi.org/10.3390/buildings12071006.

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This study used model experiments and numerical simulations to investigate the backlayering length of a vehicle-blocked tunnel fire. The experimental setup included two types of obstacles (low obstacles and high obstacles), as well as three configurations: no obstacles, one side with a car obstacle, and two sides with a car obstacle. If there were vehicles on one side of a lane, it would have little effect on the elongation of the backlayer length. When there were vehicles on both sides of a lane, the elongation of the backlayer length was greatly reduced. In addition, the effects of the vehicular blockage ratio and blockage configuration on the properties of the backlayering length were investigated. We created Pattern A, where fire is was in the center, and Pattern B, where fire was on the side of the tunnel. In Pattern A, almost all obstacles could be approximated using the formula. When the vehicle blockage ratio of a single lane was small, an approximation formula for Pattern B was applicable. However, if the distance between stationary vehicles on the upstream side of the fire source was small, the backlayering length could have been longer than in the case with no vehicular blockage.

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3

Hansen, Rickard. "The Throttle Effect – Blower Fan Versus Exhaust Fan." Mining Revue 28, no. 3 (September 1, 2022): 1–20. http://dx.doi.org/10.2478/minrv-2022-0016.

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Abstract One of the risks connected to fires underground is the throttle effect which may cause unforeseen smoke spread. This paper investigates the throttle effect for a blower fan and an exhaust fan case in a mine drift. The aim of the paper is to perform a parametric study on the throttle effect, varying influencing parameters such as the heat release rate and fan flow velocity. Data from fire experiments in a model-scale mine drift and results from CFD simulations were used during the study. It was found that the differences between the two fan cases were significant both in magnitude and occasionally in direction. For the base cases the throttle effect as well as the backlayering were more severe in the exhaust fan case. When increasing the heat release rate to 116 kW an increasing backlayering resulted, but the throttle effect was found to increase for the exhaust fan case and decrease for the blower fan case. The throttle effect decreased in the blower fan case as the gas density decrease levelled off, but the flow velocity increased even further, causing an increase in the downstream mass flow rate. This finding was confirmed by similar experimental results in model-scale mine drifts. The resulting mass flow rate induced by the fire plume changes was found to be higher than the externally imposed increase of the fan flow velocity. When increasing the distance between the fire and the exhaust fan, the backlayering increased and the throttle effect decreased.

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4

Haddad, Razieh Khaksari, Cristian Maluk, Eslam Reda, and Zambri Harun. "Critical Velocity and Backlayering Conditions in Rail Tunnel Fires: State-of-the-Art Review." Journal of Combustion 2019 (May 28, 2019): 1–20. http://dx.doi.org/10.1155/2019/3510245.

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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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5

Zhao, Hong Li, Zhi Sheng Xu, and Xue Peng Jiang. "Reduced-Scale Model Tests of Fires in Railway Tunnel and Structure Fire Safety." Advanced Materials Research 168-170 (December 2010): 2473–76. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.2473.

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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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6

Ko, Yoon J., and George V. Hadjisophocleous. "Study of smoke backlayering during suppression in tunnels." Fire Safety Journal 58 (May 2013): 240–47. http://dx.doi.org/10.1016/j.firesaf.2013.03.001.

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7

FUJITA, Katsushi, Tomoya MINEHIRO, Nobuyoshi KAWABATA, and Futoshi TANAKA. "Temperature Characteristics of Backlayering Thermal Fumes in a Tunnel Fire." Journal of Fluid Science and Technology 7, no. 3 (2012): 275–89. http://dx.doi.org/10.1299/jfst.7.275.

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8

Ilias, Nicolae, Omar Lanchava, Giorgi Nozadze, and David Tsanava. "Study of propagation of harmful factors of fire in short road tunnels with different inclinations." MATEC Web of Conferences 342 (2021): 03023. http://dx.doi.org/10.1051/matecconf/202134203023.

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The paper considers the spread of combustion products caused by fires with different heat release rates: 5, 10, 15, 20, 30, 50 MW in up to 400 m long tunnels. The slope of the tunnels on numerical models is - 0, 1, 3, 5, 7, 9%. The cross-sectional area of the tunnel is 42.5m2. The paper describes the dynamic variability of damaging factors caused by the “chimney effect” such as carbon monoxide and temperature. Modeling was done with FDS software by using the finite volume method. The time of process modeling is 180 s. The minimum cell size of the finite volume is 0.25x 0.25 x 0.25m. The hearth of fire is in the central part of the tunnel. The obtained results are given in the plane of the central longitudinal section of the tunnel. The boundary condition is given as an increment of the dynamic pressure caused by the height difference between the portals in normal conditions. The dependence of fire-induced backlayering distance on the fire heat release rate and the increment of the dynamic pressure caused by tunnel inclination are studied. The theoretical results and those obtained by modeling of the backlayering distance and velocity are analyzed and compared. The locations of high-risk factors for each damaging factor along the tunnel are identified. Their quasi-stationary nature is described and the intervals of transient processes typical to each factor are determined in the course of modeling. It is advisable to use the obtained results to respond to emergencies caused by fire in relevant tunnels.

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9

Weng, Miao-cheng, Xin-ling Lu, Fang Liu, Xiang-peng Shi, and Long-xing Yu. "Prediction of backlayering length and critical velocity in metro tunnel fires." Tunnelling and Underground Space Technology 47 (March 2015): 64–72. http://dx.doi.org/10.1016/j.tust.2014.12.010.

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10

ISHIKAWA, Masao, Nobuyoshi KAWABATA, Takuji ISHIKAWA, and Yuko KUNIKANE. "K-1034 Backlayering Velocity of the Thermal Plume Induced by Tunnel Fires." Proceedings of the JSME annual meeting II.01.1 (2001): 9–10. http://dx.doi.org/10.1299/jsmemecjo.ii.01.1.0_9.

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11

Li, Ying Zhen, Bo Lei, and Haukur Ingason. "Study of critical velocity and backlayering length in longitudinally ventilated tunnel fires." Fire Safety Journal 45, no. 6-8 (November 2010): 361–70. http://dx.doi.org/10.1016/j.firesaf.2010.07.003.

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12

Gannouni, Soufien, and Rejeb Ben Maad. "CFD analysis of smoke backlayering dispersion in tunnel fires with longitudinal ventilation." Fire and Materials 41, no. 6 (August 26, 2016): 598–613. http://dx.doi.org/10.1002/fam.2394.

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13

Tilley, N., and B. Merci. "Relation between horizontal ventilation velocity and backlayering distance in large closed car parks." Fire Safety Science 9 (2008): 777–87. http://dx.doi.org/10.3801/iafss.fss.9-777.

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14

Vauquelin, O. "(Experimental characterization of backlayering occurrence) (Caracterisation experimentale de l'apparition d'une nappe de retour)." International Journal of Multiphase Flow 22 (December 1996): 105. http://dx.doi.org/10.1016/s0301-9322(97)88230-4.

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15

Du, Tao, Jiaxing Du, Dong Yang, Song Dong, and Lingling Yang. "Transient evolution and backlayering of buoyancy-driven contaminants in a narrow inclined space." Building and Environment 143 (October 2018): 59–70. http://dx.doi.org/10.1016/j.buildenv.2018.06.050.

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16

FUJITA, Katsushi, Tomoya MINEHIRO, Nobuyoshi KAWABATA, and Futoshi TANAKA. "Model Experiment on Temperature Distribution of Backlayering Thermal Fume in Tunnel Fires(Fluids Engineering)." Transactions of the Japan Society of Mechanical Engineers Series B 76, no. 768 (2010): 1176–83. http://dx.doi.org/10.1299/kikaib.76.768_1176.

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17

MINEHIRO, Tomoya, Katsushi FUJITA, Nobuyoshi KAWABATA, Masato HASEGAWA, and Futoshi TANAKA. "Backlayering Distance of Thermal Fume in Tunnel Fires (Fire Experiment Using a Model Tunnel)." TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B 77, no. 776 (2011): 1064–74. http://dx.doi.org/10.1299/kikaib.77.1064.

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18

Du, Tao, Dong Yang, and Yao Ding. "Driving force for preventing smoke backlayering in downhill tunnel fires using forced longitudinal ventilation." Tunnelling and Underground Space Technology 79 (September 2018): 76–82. http://dx.doi.org/10.1016/j.tust.2018.05.005.

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19

HAYASHI, Takumi, Noboyoshi KAWABATA, Takkuji ISHIKAWA, and Tetsuharu MATSUMOTO. "K-1035 Influence of Obstacle on Backlayering Characteristic of Thermal Plume in Model Tunnel." Proceedings of the JSME annual meeting II.01.1 (2001): 11–12. http://dx.doi.org/10.1299/jsmemecjo.ii.01.1.0_11.

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20

MINEHIRO, Tomoya, Katsushi FUJITA, Nobuyoshi KAWABATA, Masato HASEGAWA, and Futoshi TANAKA. "Backlayering Distance of Thermal Fumes in Tunnel Fire Experiments Using a Large-Scale Model." Journal of Fluid Science and Technology 7, no. 3 (2012): 389–404. http://dx.doi.org/10.1299/jfst.7.389.

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21

Huang, Youbo, Xi Liu, Bingyan Dong, Hua Zhong, Bin Wang, and Qiwei Dong. "Effect of inclined mainline on smoke backlayering length in a naturally branched tunnel fire." Tunnelling and Underground Space Technology 134 (April 2023): 104985. http://dx.doi.org/10.1016/j.tust.2023.104985.

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22

Weisenpacher, P., J. Glasa, L. Valasek, and T. Kubisova. "FDS simulation of smoke backlayering in emergency lay-by of a road tunnel with longitudinal ventilation." Journal of Physics: Conference Series 2090, no. 1 (November 1, 2021): 012100. http://dx.doi.org/10.1088/1742-6596/2090/1/012100.

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Abstract This paper investigates smoke movement and its stratification in a lay-by of a 900 m long road tunnel by computer simulation using Fire Dynamics Simulator. The lay-by is located upstream of the fire in its vicinity. The influence of lay-by geometry on smoke spread is evaluated by comparison with a fictional tunnel without lay-by. Several fire scenarios with various tunnel slopes and heat release rates of fire in the tunnels without and with the lay-by are considered. The most significant breaking of smoke stratification and decrease of visibility in the area of the lay-by can be observed in the case of zero slope tunnel for more intensive fires with significant length of backlayering. Several other features of smoke spread in the lay-by are analysed as well. The parallel calculations were performed on a high-performance computer cluster.

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23

Ha, Yejin, and Joonho Jeon. "A Numerical Study on the Smoke Control System Performance for a Large Fire in a Long Tunnel." Fire Science and Engineering 36, no. 6 (December 31, 2022): 48–61. http://dx.doi.org/10.7731/kifse.bf751a22.

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In this study, a numerical simulation was performed using the fire dynamics simulator to examine the performance of a smoke control system in the case of a large fire in a long tunnel. A regional long tunnel that facilitates frequent movement in the port area was simulated. The fire scenario was set as a heavy goods vehicle fire corresponding to a large fire based on the existing real-scale experimental research data. A jet fan with an inner diameter of 1250 mm used in the regional tunnel was included in the tunnel simulation. For the evaluation of the smoke control system performance, the effects of the flow rate and installation interval of the jet fan on the smoke behavior, visibility, and temperature was analyzed. As the flow rate of the jet fan decreased, backlayering was lengthened, which reduced the time to achieve life safety standard.

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24

Du, Tao, Ping Li, Haibin Wei, and Dong Yang. "On the backlayering length of the buoyant smoke in inclined tunnel fires under natural ventilation." Case Studies in Thermal Engineering 39 (November 2022): 102455. http://dx.doi.org/10.1016/j.csite.2022.102455.

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25

HAYASHI, Takumi, Nobuyoshi KAWABATA, Takuji ISHIKAWA, and Tetsuharu MATSUMOTO. "Influence of the Obstacle on the Backlayering Characteristic of the Thermal Plume in a Tunnel." Proceedings of Conference of Hokuriku-Shinetsu Branch 2002.39 (2002): 83–84. http://dx.doi.org/10.1299/jsmehs.2002.39.83.

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26

MINEHIRO, Tomoya, Nobuyoshi KAWABATA, and Katsushi FUJITA. "S0503-2-6 Backlayering Characteristics of Thermal Fume in Tunnel Fires that used Numerical Simulation." Proceedings of the JSME annual meeting 2009.2 (2009): 153–54. http://dx.doi.org/10.1299/jsmemecjo.2009.2.0_153.

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27

WANG, Qian, Nobuyoshi KAWABATA, and Takuji ISHIKAWA. "Evaluation of Critical Velocity Employed to Prevent the Backlayering of Thermal Fume during Tunnel Fires." Transactions of the Japan Society of Mechanical Engineers Series B 67, no. 656 (2001): 911–18. http://dx.doi.org/10.1299/kikaib.67.911.

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28

Fan, Chuan Gang, and Jian Yang. "Experimental study on thermal smoke backlayering length with an impinging flame under the tunnel ceiling." Experimental Thermal and Fluid Science 82 (April 2017): 262–68. http://dx.doi.org/10.1016/j.expthermflusci.2016.11.019.

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29

Du, Tao, Lingling Yang, Dong Yang, Song Dong, and Wenhui Ji. "On the backlayering flow of the buoyant contaminants in a tunnel with forced longitudinal ventilation." Building and Environment 175 (May 2020): 106798. http://dx.doi.org/10.1016/j.buildenv.2020.106798.

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30

KUNIKANE, Yuko, Nobuyoshi KAWABATA, Takaaki YAMADA, and Akifumi SHIMODA. "Influence of Stationary Vehicles on Backlayering Characteristics of Fire Plume in a Large Cross Section Tunnel." JSME International Journal Series B 49, no. 3 (2006): 594–600. http://dx.doi.org/10.1299/jsmeb.49.594.

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31

Tilley, Nele, Xavier Deckers, and Bart Merci. "CFD study of relation between ventilation velocity and smoke backlayering distance in large closed car parks." Fire Safety Journal 48 (February 2012): 11–20. http://dx.doi.org/10.1016/j.firesaf.2011.12.005.

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32

Meng, Na, Xiaomei Liu, Xiao Li, and Beibei Liu. "Effect of blockage ratio on backlayering length of thermal smoke flow in a longitudinally ventilated tunnel." Applied Thermal Engineering 132 (March 2018): 1–7. http://dx.doi.org/10.1016/j.applthermaleng.2017.12.064.

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33

Tian, Mengya, Guangli Lu, Beibei Liu, and Jianfeng Zhao. "Numerical Simulation Study on the Laws of Smoke Backlayering of Fire in Level Roadway of Metal Mine." IOP Conference Series: Earth and Environmental Science 558 (September 5, 2020): 022030. http://dx.doi.org/10.1088/1755-1315/558/2/022030.

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34

Ko, Yoon J., and George V. Hadjisophocleous. "Corrigendum to “Study of smoke backlayering during suppression in tunnels” Fire Safe. J. 58 (2013) 240–247." Fire Safety Journal 68 (August 2014): 129. http://dx.doi.org/10.1016/j.firesaf.2014.07.005.

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35

Weisenpacher, Peter, Jan Glasa, and Lukas Valasek. "Influence of slope and external temperature on smoke stratification in case of fire in bi-directional road tunnel." ITM Web of Conferences 16 (2018): 02002. http://dx.doi.org/10.1051/itmconf/20181602002.

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Jet fan ventilation strategy in case of fire in bi-directional road tunnels is focused on maintaining smoke stratification. There are several factors influencing stratification under specific conditions. In this paper smoke movement during a 5 MW fire in a 600 m long road tunnel is studied by computer simulation and the influence of slope and external temperature on smoke stratification is analysed. Calculations were performed on a high performance computer cluster using parallel version of Fire Dynamics Simulator. Smoke stratification upstream of the fire is maintained in every simulation scenario with the exception of declivous tunnel, in which buoyancy intensifies backlayering. The behaviour of the smoke movement downstream of the fire is more complex. In the case of horizontal tunnel the stratification is not maintained in the vicinity of the fire and region with untenable conditions expands downstream. In the tunnel with slope of -2° this expansion is accelerated, while in the tunnel with slope of 2° untenable conditions spread in opposite direction. The influence of exterior temperature higher than temperature inside the tunnel is relatively weak in horizontal tunnels; however, it becomes very important in sloping tunnels, especially downstream of the fire.

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36

MINEHIRO, Tomoya, Katsushi FUJITA, and Nobuyoshi KAWABATA. "600 Backlayering Characteristics of Thermal Fume in Tunnel Fires : Model Experiment concerning relationship between Longitudinal Velocity and Distance." Proceedings of Conference of Hokuriku-Shinetsu Branch 2008.45 (2008): 173–74. http://dx.doi.org/10.1299/jsmehs.2008.45.173.

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37

Gannouni, Soufien, and Rejeb Ben Maad. "Numerical study of the effect of blockage on critical velocity and backlayering length in longitudinally ventilated tunnel fires." Tunnelling and Underground Space Technology 48 (April 2015): 147–55. http://dx.doi.org/10.1016/j.tust.2015.03.003.

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38

Haddad, Razieh Khaksari, Zambri Harun, Cristian Maluk, and M. Rasidi Rasani. "XPERIMENTAL STUDY OF THE INFLUENCE OF BLOCKAGE ON CRITICAL VELOCITY AND BACKLAYERING LENGTH IN A LONGITUDINALLY VENTILATED TUNNEL." JP Journal of Heat and Mass Transfer 17, no. 2 (August 20, 2019): 451–76. http://dx.doi.org/10.17654/hm017020451.

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39

Meng, Na. "Experimental study on flame merging behaviors and smoke backlayering length of two fires in a longitudinally ventilated tunnel." Tunnelling and Underground Space Technology 137 (July 2023): 105147. http://dx.doi.org/10.1016/j.tust.2023.105147.

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40

Sekularac, Milan, Novica Jankovic, and Petar Vukoslavcevic. "Ventilation performance and pollutant flow in a unidirectional-traffic road tunnel." Thermal Science 21, suppl. 3 (2017): 783–94. http://dx.doi.org/10.2298/tsci160321117s.

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To develop a reliable method for modeling fire case scenarios within the road tunnels and observing the effects of the skewed velocity, experimental and numerical approach is used. Experimental results obtained from a laboratory tunnel model installation, are used to define geometry and boundary conditions. The result for the overall ventilation performance is compared to the available cases, for empty tunnel and stationary bi-directional vehicle traffic. For a unidirectional traffic road tunnel, in traffic loaded conditions, with a ventilation system based on axial ducted fans, the numerical simulation is used to determine the flow and temperature fields, the ventilation efficiency (efficiency of momentum transfer), and to assess the shape of the velocity distribution. The effect that a skewed velocity distribution can have on the resulting thermal and pollutant fields (CO2), smoke backlayering and stratification, is evaluated using numerical simulations, for the model-scale tunnel fire conditions. The effect of two possible limiting shapes of the velocity distribution, dependent only on the location of the fire with respect to the nearest upstream operating fans, is analyzed. The numerical results for a fire are scenario are a starting point in assessing the feasibility of a laboratory model fire-scenario experiment, what is planned as the next step in this research.

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41

Tanaka, Futoshi, Kohei Takezawa, Yuji Hashimoto, and Khalid A. M. Moinuddin. "Critical velocity and backlayering distance in tunnel fires with longitudinal ventilation taking thermal properties of wall materials into consideration." Tunnelling and Underground Space Technology 75 (May 2018): 36–42. http://dx.doi.org/10.1016/j.tust.2017.12.020.

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42

Huang, Youbo, Yanfeng Li, Junmei Li, Jiaxin Li, Ke Wu, Kai Zhu, and Haihang Li. "Modelling and experimental investigation of critical velocity and driving force for preventing smoke backlayering in a branched tunnel fire." Tunnelling and Underground Space Technology 99 (May 2020): 103388. http://dx.doi.org/10.1016/j.tust.2020.103388.

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43

Gannouni, Soufien. "Critical velocity for preventing thermal backlayering flow in tunnel fire using longitudinal ventilation system: Effect of floor-fire separation distance." International Journal of Thermal Sciences 171 (January 2022): 107192. http://dx.doi.org/10.1016/j.ijthermalsci.2021.107192.

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44

Guo, Fangyi, Zihe Gao, Huaxian Wan, Jie Ji, Longxing Yu, and Long Ding. "Influence of ambient pressure on critical ventilation velocity and backlayering distance of thermal driven smoke in tunnels with longitudinal ventilation." International Journal of Thermal Sciences 145 (November 2019): 105989. http://dx.doi.org/10.1016/j.ijthermalsci.2019.105989.

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45

Meng, Na, Wenyu Yang, Lin Xin, Xiao Li, Beibei Liu, and Xiaona Jin. "Experimental study on backlayering length of thermal smoke flow in a longitudinally ventilated tunnel with blockage at upstream of fire source." Tunnelling and Underground Space Technology 82 (December 2018): 315–24. http://dx.doi.org/10.1016/j.tust.2018.08.034.

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46

Yao, Yongzheng, Baolin Qu, Hongqing Zhu, Jingxin Wang, Shengzhong Zhao, and Qiang Wang. "Theoretical and numerical study on critical velocity and driving force for preventing smoke backlayering in a connection roadway fire of coal mines." Tunnelling and Underground Space Technology 127 (September 2022): 104566. http://dx.doi.org/10.1016/j.tust.2022.104566.

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47

"Analysis of critical air velocity in a road tunnel fire." Journal of the Croatian Association of Civil Engineers 74, no. 11 (December 2022): 979–86. http://dx.doi.org/10.14256/jce.3515.2022.

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A critical air velocity analysis was performed using a numerical model adapted for the eastern tunnel tube of the Kastelec road tunnel in Slovenia. This allowed the efficiency of the fans to be tested, which is required to maintain appropriate traffic conditions and prescribed safety in the tunnel. At the critical air velocity, that is, at an air velocity lower than the prescribed one, where the spread of smoke can still be effectively controlled to ensure time for a safe evacuation of passengers from a fire-endangered tunnel tube, special attention was paid to the phenomena of smoke backlayering and layered spread of smoke under the tunnel ceiling (so-called “stratification”). Simulations of the longitudinal ventilation system with single point extractions were conducted.

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48

Lanchava, Omar, Nicolae Ilias, Sorin Mihai Radu, Giorgi Nozadze, and Marad Jangidze. "A SYSTEM OF TRANSFORMABLE CROSSPIECES TO BLOCK HARMFUL COMBUSTION PRODUCT PROPAGATION IN TUNNELS." GEORGIAN SCIENTISTS, May 26, 2021. http://dx.doi.org/10.52340/gs.02.09.233.

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Controlling the events and processes caused by fires is one of the key issues of all projects dedicated to the fire safety of tunnels. These processes are characterized by the dynamics of the propagation of high temperature, smoke and toxic combustion products around the seat of fire and in tunnels. With longitudinal ventilation, two main parameters are to be considered: the critical velocity and the backlayering length. An important impact on both parameters is exerted by the proposed system of flexible crosspieces, which, by increasing the aerodynamic resistance of a tunnel, makes it possible to reduce the speed of propagation of harmful factors of fire through the tunnel. Moreover, with certain limitations, the given crosspieces can be used to divide the tunnel into small sections what, among other things, will hinder the propagation of fire for a certain time. Thorough theoretical and experimental study of the mentioned transformable crosspieces, as well as the development of their various structures and operating principles is necessary to ensure the safety of traffic tunnels. The present article proposes a novel technology of light transformable crosspieces, which can be used in both, the existing road tunnels and the ones planned to design.

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49

LANCHAVA, Omar, Nicolae ILIAS, Sorin Mihai RADU, Leon MAKHARADZE, Teimuraz KUNCHULIA, Nino ARUDASHVILI, and Zaza KHOKERASHVILI. "ANALYSIS OF THE PARAMETERS OF THE FIRE MODELED IN A ROAD TUNNEL." GEORGIAN SCIENTISTS, June 26, 2021. http://dx.doi.org/10.52340/gs.02.09.235.

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Abstract:

The essence of the problem lies in the experimental study of the laws governing the changes in the aerodynamics of air flow and the most important ventilation parameters, taking into account the effect of fire. During the experiments, the aerodynamics of the tunnel is complicated by the presence of additional resistance, and the variables will be: the slope of the tunnel, the heat release rate, the cross section of the tunnel, the ratio of the width of the tunnel to the height, the fill factor of the tunnel by transport. The solution to the problem is an improved ventilation technology in case of fires to save lives. The aim of the research is to study the critical velocity, the backlayering length and the gradient-factor using numerical and physical models, as well as mathematical analysis for the downward movement of fresh air, when the fresh air inlet is above the fire level. The scale of the physical models is 1:40 and 1:60. Numerical models are full scale using of modern engineering technique Pyrosim and Fluent. The generalization of the results is carried out using piece-wise constant functions. The obtained results are also be compared with similar results known from scientific literature.

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50

Khokerashvili, Zaza, and Davit Tsanava. "Propagation of carbon monoxide in road tunnels in case of fire by considering the critical velocity, backlayering and gradient factor." GEORGIAN SCIENTISTS, May 18, 2022. http://dx.doi.org/10.52340/gs.2022.04.03.07.

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