Effect of longitudinal slope on the smoke propagation and ceiling temperature characterization in sloping tunnel fires under natural ventilation

Gao, Zihe; Li, Linjie; Sun, Changchun; Wang, Zhong; Yan, Changbin

doi:10.1016/j.tust.2022.104396

Cited by 47 publications

(14 citation statements)

References 32 publications

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“…The dimensionless HRR of Q˙ is described by equation (2) 8,19 where Q˙ is the HRR of a single fire source (kW), n is the combustion efficiency and the value is 1, m˙f is the mass flow rate of propane fuel (m 3 /h), ΔHc is the combustion heat of propane (46.3 MJ/kg), trueQ˙total is the total HRR of two fire sources (kW), ρ∞ is the air density (1.21 kg/m 3 ), Cp is the specific heat capacity of air (1.004 kJ/(kg•K)), T∞ is the air temperature (303 K), g is the acceleration of gravity (9.8 m/s 2 ), d is the length of the short side of the rectangular fire source (m) and w is the length of the long side of a rectangular fire source (m). The corresponding dimensionless HRR of Q˙ are 0.28, 0.43, 0.71, 0.99 and 1.28, respectively.…”

Section: Experimental Setupsmentioning

confidence: 99%

“…6 In previous works, many scholars have done some research on fire in tunnels by experiment and numerical simulation. [7][8][9] To study intense burning behaviour caused by multiple fires in a tunnel, such as fire merging, He et al 10 studied the characteristics and hazards of multi-pool fires in the tunnel under natural ventilation condition through a series of experiments. Chen et al 11 established the heat flow distribution relationship under the tunnel ceiling through experiments and concluded that the tunnel sidewalls would increase the thermal heat feedback and the ceiling heat flow.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study on the flame merging and ceiling impingement behavior of transversely located double fire sources in an urban utility tunnel

Zhang

Gao

et al. 2023

Indoor and Built Environment

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The investigation of the fire characteristics and propagation behaviour in the urban utility tunnel is of great practical importance, especially for the conditions with double fire sources. In this work, a 1/8th scaled urban utility tunnel model was built to conduct the experiments to characterize the flame merging and ceiling impingement behaviour of transversely located double fire sources. Two rectangular fire sources with the same dimension were used, and their heat release rate (HRR) and fire source spacings were varied to consider the typical scenarios. Results show that for the smaller HRR, the tunnel ceiling and sidewalls have little influence on the flame merging of double fire sources. With the increase of HRR, the flame gradually impinges on the tunnel ceiling and forms a stable ceiling jet flame extension, and the ceiling and sidewalls of the tunnel can promote the merging of the flames of the double fire sources. Besides, with the increase of the fire source spacings, the flame merging probability P m can be divided into three stages, that is, (i) complete merging stage, (ii) intermittent merging stage and (iii) complete separation stage. On this basis, the predicting relation of P m was obtained by using the piecewise function.

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Section: Experimental Setupsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental study on the flame merging and ceiling impingement behavior of transversely located double fire sources in an urban utility tunnel

Zhang

Gao

et al. 2023

Indoor and Built Environment

Self Cite

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“…29 Moreover, its capacity to simulate various building fire scenarios has been widely verified through multi-scale fire experiments. 33,34…”

Section: Numerical Simulationmentioning

confidence: 99%

“…29 Moreover, its capacity to simulate various building fire scenarios has been widely verified through multi-scale fire experiments. 33,34 FDS employs numerical methods to solve a variant of the Navier-Stokes equations governing thermally-driven flow. It incorporates both the DNS (Direct Numerical Simulation) model and the LES (Large Eddy Simulation) model.…”

Section: Fire Dynamics Simulatormentioning

confidence: 99%

Investigation of the fire hazard of underground space fire scenarios in urban metro tunnels under natural ventilation: Analysis of the impact of tunnel slope on smoke back-layering length

Su,

Li,

Zhong

et al. 2023

Building Services Engineering Research and Technology

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The smoke back-layering length is a crucial parameter for evacuating people in both road and subway tunnel fires. This study investigates the fire hazard induced by carriage fire in inclined metro tunnels under natural ventilation. The parameter ‘transition slope’ is defined to measure the smoke flow from the carriage head in the upstream direction to the tunnel or not due to the stack effect of the tunnel slope. The aim of this paper is to analyse the effects of changes in cross-section, downstream length, tunnel slope, and carriage side-door coupling on smoke behaviour characteristics by experiment and simulation methods. A piecewise function expression between dimensionless smoke back-layering length, downstream length, and tunnel slope for carriage fires in an inclined tunnel under natural ventilation is proposed by theoretical analysis. At the same time, a 1:15 scale model experiment was conducted to initially analyse the characteristics of smoke movement. Following this, full-scale numerical simulations were employed to complement the model experiment and quantify the principles governing smoke movement. The experimental results show that the tunnel slope has a significant effect on the smoke back-layering length. In contrast, the influence of the heat release rate was found to be relatively minor. In addition, simulation results show that the tunnel slope has no significant effect on the smoke back-layering length when the fire location is approximately 20 m from the train head, and the tunnel slope is in the range of 2.29° ∼ 3.43° (4% ∼ 6%). For small tunnel slopes, smoke spreads in the tunnel, and the smoke back-layering length produced by the virtual fire source shows a different law from the previous study model. Finally, the correlation coefficient of the piecewise function in theoretical analysis is fitted by combining the experimental and numerical simulation results. Practical application This study provides valuable insights into the practical implications of controlling and mitigating the impact of fires in inclined metro tunnels. By understanding the critical role of tunnel slope and providing a quantitative tool for smoke spread law assessment, this study contributes to the enhancement of safety measures and the protection of lives in tunnel environments during fire incidents.

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“…Where Chow et al 21 . used a 1/50 tunnel model with an adjustable angle to learn the re smoke dispersion pattern under 5°, 10° and 15°s lopes; Lei 22 used numerical simulation with branch slopes of 0%, 3%, 6%, and 9% to estimate the mass and heat ux into the branch; Gao et al 23 . learned the effect of longitudinal slope on the smoke propagation and ceiling temperature characterization in sloping tunnel res under natural ventilation; Tao et al 24,25 .…”

Section: Introductionmentioning

confidence: 99%

Experimental study on the influence of longitudinal slope on airflow-dust migration behavior after tunnel blasting

Tao

Zhang

et al. 2023

Preprint

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In this paper, a 1:21 model experiment was conducted to discuss the dust dispersion efficiency and liner trolley obstruction effect inside the tunnel at -9° to 9°, the effect of different initial dust concentrations on dust dispersion and liner trolley obstruction effect at 6° slope, and the effect of different return air velocity on dust dispersion at 6° slope. The results show that as the slope of the tunnel changes from 0° to -9°, the average dust dispersion time decreases by 3.7% at the working face and the dust concentration difference between the front and rear of the trolley is improved by 2.7%. When the slope of the tunnel changes from 0° to -9°, the average dust dispersion time increases by 7.2% at the working face and the dust concentration difference between the front and rear of the trolley is improved by 17.9%. With each 100mg/m3 increase in the initial dust concentration, the dust dispersion time at the working face and the tunnel exit increases by 9.15% and 8.17% on average, and the lining trolley obstruction time increases by 23.33s on average. The dust dispersion times take an average reduction rate of 15.7%, with the increase of return air velocity. The recommended return air velocity is greater than 1m/s for large slope tunnels. When the slope changes from 0°to 9°, the hindrance rate of slope on dust dispersion is 2.88462%, 8.65385%, and 16.34615% respectively. Dust dispersion efficiency will be reduced as the tunnel slope changes from 0°to 9°, The growth rate of slope on dust dispersion is -0.96154%, -2.88462%, and -6.73077% respectively.

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Effect of longitudinal slope on the smoke propagation and ceiling temperature characterization in sloping tunnel fires under natural ventilation

Cited by 47 publications

References 32 publications

Experimental study on the flame merging and ceiling impingement behavior of transversely located double fire sources in an urban utility tunnel

Experimental study on the flame merging and ceiling impingement behavior of transversely located double fire sources in an urban utility tunnel

Investigation of the fire hazard of underground space fire scenarios in urban metro tunnels under natural ventilation: Analysis of the impact of tunnel slope on smoke back-layering length

Experimental study on the influence of longitudinal slope on airflow-dust migration behavior after tunnel blasting

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