Prediction of smoke back-layering length under different longitudinal ventilations in the subway tunnel with metro train

Zhang, Shaogang; Wu, Bing; Zhu, Kai; Li, Kaiyuan; Zhang, Ruifang; Lu, Song; Cheng, Xudong

doi:10.1016/j.tust.2015.12.013

Cited by 73 publications

(46 citation statements)

References 22 publications

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“…13 This is because a blockage in the upstream of the fire source can alter the smoke movement and, consequently, the ventilation requirements of the tunnel. 26,27 To reduce the amount of mesh cells and improve the resolution of the flow field, the Froude modeling strategy has been adopted by this study. 25 The code has been widely used in the fire research field, and its validity has been extensively verified.…”

Section: Introductionmentioning

confidence: 99%

“…26,27 To reduce the amount of mesh cells and improve the resolution of the flow field, the Froude modeling strategy has been adopted by this study. 26,29 The layout of the measuring points is presented in Figure 1. In different blockage scenarios, the blockage height is fixed as 0.35 m while the blockage width is ranged from 0.875 to 1.375 m. Table 1 lists all the detailed simulation cases.…”

Section: Introductionmentioning

confidence: 99%

“…In the first nine cases, the passenger blockage was not included, and these cases were mainly used for model validation. 26 In FDS, D * is used primarily to judge the mesh quality, which is The effects of passenger blockage ratio on smoke flow properties with the fixed blockage length were studied by the cases 37 to 54.…”

Section: Introductionmentioning

confidence: 99%

“…26,30 In this study, the lowest heat release rate is 50 kW, and the value of 0.1D * is approximately 0.03 m. To evaluate the mesh independence, three mesh sizes are tested and compared. 26,30 In this study, the lowest heat release rate is 50 kW, and the value of 0.1D * is approximately 0.03 m. To evaluate the mesh independence, three mesh sizes are tested and compared.…”

Section: Introductionmentioning

confidence: 99%

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Effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires

Wang

2019

Fire and Materials

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This paper investigates the effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires. A series of numerical simulations were conducted in a 1/5 small-scale tunnel with the different heat release rates (50-100 kW), longitudinal ventilation velocities (0.5-1 m/s), passenger blockage lengths (2-6 m), and ratios (0.17-0.267). The typical smoke flow properties in different tunnel fire scenarios are analyzed, and the results show that under the same heat release rate and longitudinal ventilation velocity, the smoke back-layering length, maximum smoke temperature, and downstream smoke layer height decrease with increasing passenger blockage length or ratio. The Li correlations can well predict the smoke backlayering length and maximum smoke temperature in tunnel fire scenarios without the passenger blockage. When the passenger blockage exists, the modified local ventilation velocity that takes the blockage length and ratio into account has been proposed to correct the Li correlations. The smoke back-layering length and maximum smoke temperature with the different blockage lengths and ratios can be predicted by the modified correlations, which are shown to well reproduce the simulation results. K E Y W O R D S passenger blockage, smoke flow, tunnel fire

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires

Wang

2019

Fire and Materials

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“…In the case of fire, the transportation of smoke along the tunnel is altered by its slope, length, traffic, etc., and the obstruction of the ventilation ports increase a different variable in the analysis of physical scenario apart from external weather conditions [17][18][19][20][21][22][23][24][25]. The complexity of the situation creates the need not only for the creation of general but for particular emergency response procedures [26].…”

Section: Introductionmentioning

confidence: 99%

CFD Simulation of Obstructed Ventilation Ports in a Subway Tunnel Section

Herrera¹,

Pineda²,

Silva-Rivera

et al. 2017

Int. j. simul. model.

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A CFD simulation of the air velocity in a subway tunnel section of 1400 m in length is presented. In this case of study; the simulation compares the air velocity changes when two of six natural ventilation ports are totally obstructed. They are required for hot air exhaust, smoke release and fresh air intake. The mechanical ventilation system is located inside the tunnel at 650 m from the end of a passenger platform and 750 m from the other, it is a non-symmetrical scenario. The simulation was carried in ANSYS® Fluent compared with NFPA calculation and considering geometries and dimensions of an actual subway section of the Mexico City. Four different numerical models were created to analyse eight different cases. The results indicate that the obstruction of the ports create a non-homogeneous distribution of the flow velocity inside the passenger platform with an approximate difference of 1.5 m/s. This value is very important in cases when the backlayering effect has to be avoided as in the case of smoke transportation, exhaust of smoke and the transport of dust or some other contaminant. The emergency procedures and the design of escape routes can be improved by considering the physical changes occurring when the ventilation ports are obstructed. Since the atmospheric pressure influence the direction and velocity of the flow coming from the non-obstructed vents.

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CFD analysis of smoke backlayering dispersion in tunnel fires with longitudinal ventilation

Gannouni¹,

Maad²

2016

Fire and Materials

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Summary In a longitudinally ventilated tunnel fire, the backlayering flow propagated in the opposite direction to the air current is the most fatal contaminations to users which are blocked upstream of the fire. In the present paper, numerical simulations were conducted using Fire Dynamic Simulator, which is based on large eddy simulations to estimate the backlayering arrival time in a longitudinally ventilated tunnel fire. The effect of a vehicle obstruction on the backlayering arrival time will be also investigated. For this, a vehicle model occupying about 31% of the tunnel cross section is simulated upstream of the fire source with its location relative to the tunnel floor is varied. The numerical investigation shows that the inertia and the buoyancy forces produced by ventilation and fire, respectively, affect the backlayering spread. The backlayering arrival time increases with the longitudinal ventilation velocity while it decreases with the fire heat release rate. When a vehicle obstruction existed within the tunnel, the numerical results show an increase of backlayering arrival time. This increase is significantly more important with the fire distance when the vehicle obstruction approaches the tunnel floor. Two correlations are developed, with and without obstruction in the tunnel, to predict the backlayering arrival time against the distance to fire. Copyright © 2016 John Wiley & Sons, Ltd.

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Prediction of smoke back-layering length under different longitudinal ventilations in the subway tunnel with metro train

Cited by 73 publications

References 22 publications

Effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires

Effects of passenger blockage on smoke flow properties in longitudinally ventilated tunnel fires

CFD Simulation of Obstructed Ventilation Ports in a Subway Tunnel Section

CFD analysis of smoke backlayering dispersion in tunnel fires with longitudinal ventilation

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