An experimental investigation on blockage effect of metro train on the smoke back-layering in subway tunnel fires

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

doi:10.1016/j.applthermaleng.2015.12.085

Cited by 91 publications

(51 citation statements)

References 23 publications

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“…It is interesting to observe the small differences in case 3, from 1.42 m/s to 1.39 m/s between the left and right sides of the tunnel. These values agree if compared with the ones obtained by Zhang [17]. In case 4, the difference is 0.1 m/s between both sides of the tunnel.…”

Section: Obtained Resultssupporting

confidence: 90%

“…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%

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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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Section: Obtained Resultssupporting

confidence: 90%

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.

View full text Add to dashboard Cite

show abstract

“…Figure 3 presents the detailed comparison results. 31 Thus, V * local can be expressed as follows: Therefore, the results of all the simulations can be regarded to be reliable.…”

Section: Model Validationmentioning

confidence: 99%

“…The blockage ratio in these cases It can be seen from Equation (1) In an ideal scenario, assuming the blockage length is extremely short, the local ventilation velocity will become 1/(1 − φ) times of that without the blockage. 31 Thus, V * local can be expressed as follows:…”

Section: Effects Of Passenger Blockage Length On Typical Smoke Flowmentioning

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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Effect of metro train on the critical driving force for preventing smoke back‐layering in tunnel fires

et al. 2021

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Summary Preventing smoke back‐layering in longitudinal‐ventilated tunnels is an important topic in handling with fires safety issues. Previous studies focused on the critical velocity, while only very few of them paid attention to how to realize this parameter, that is, in a critical state, to overcome the resistance of the tunnel and the fire source to the airflow, the required driving force provided by the ventilation equipment installed in the tunnel. This study addressed this problem in the situation where the coupling effect of blockage and throttling effect was highlighted by conducting theoretical analysis and numerical simulations. The results showed that the presence of metro train blockage reduces the effective cross‐sectional area of the tunnel near the fire source and decreases the critical velocity. On the other hand, the blockage of trains also increases the resistance to the ventilation airflow and exacerbates the throttling effect, leading to the increase of the critical driving force. In such conditions, a stronger driving force to approach the critical velocity was needed. Besides, the length of train blockage was verified to exert limited influence on the value of critical velocity while it significantly affected the critical driving force. Furthermore, the calculated formula for the critical driving force was proposed with the prevention of smoke back‐layering considering the blockage effect to be emphasized.

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An experimental investigation on blockage effect of metro train on the smoke back-layering in subway tunnel fires

Cited by 91 publications

References 23 publications

CFD Simulation of Obstructed Ventilation Ports in a Subway Tunnel Section

CFD Simulation of Obstructed Ventilation Ports in a Subway Tunnel Section

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

Effect of metro train on the critical driving force for preventing smoke back‐layering in tunnel fires

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