A study on ceiling jet characteristics in an inclined tunnel

Yan, Huijie; Ye, Gao; Chow, Wan Ki

doi:10.1016/j.tust.2015.06.009

Cited by 50 publications

(6 citation statements)

References 22 publications

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“…Hinkley et al 16 studied the flames spreading beneath both combustible and non‐combustible corridor ceilings. For an inclined ceiling, Huo et al 17 studied the ceiling jet in an inclined tunnel and proposed empirical equations for gas temperature and flow velocity along the tunnel. Zhang et al 18 carried out experiments and studied the flame extension lengths induced by rectangular fire sources, and further characterized 19 the temperature distribution on the ceiling, induced by fire plume impingement, along the upstream and downstream direction from a fire.…”

Section: Introductionmentioning

confidence: 99%

Experimental study and analysis of radiation heat fluxes received by a floor beneath an inclined ceiling

et al. 2020

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Summary This study experimentally investigates the radiation heat flux distribution received on the floor due to fire plume impinging upon an inclined ceiling, which has not been quantified previously. The radiation heat fluxes were measured on the floor for 160 experimental conditions, involving various fire source heat release rates, source‐ceiling heights, angles of ceiling inclination and dimensions (aspect ratios) of the rectangular sources. The main findings include that the declining rate of the radiation heat flux along with distance received by the downstream floor decreases, while that received by the upstream floor increases, with the increasing of ceiling inclination angle. The radiation heat flux received by the floor is higher as the ceiling inclination angle is smaller for the downstream side, while it is lower as the ceiling inclination angle is smaller for the upstream side. Both of these variations can be explained by change of the flow distribution as well as flame length due to combustion and heat released in the two directions beneath the inclined ceiling. Further, a model with various fire source heat release rates, source‐ceiling height, and ceiling inclination angles is proposed, to globally describe the radiation heat flux received by both the upstream and downstream floors.

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Section: Introductionmentioning

confidence: 99%

Experimental study and analysis of radiation heat fluxes received by a floor beneath an inclined ceiling

et al. 2020

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“…The maximum temperature at 10 mm below the ceiling for the transitional behavior is obtained using the following equations presented by Huo et al [20]:…”

Section: Upper Layer Temperaturementioning

confidence: 99%

The Contamination of the Lower Layer in Sloped Tunnel Fires

Ortega

Viegas

Coelho

2023

Fire

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Fires in tunnels are a major concern due to the casualties they may cause. Therefore, forced ventilation is mandatory in long tunnels, despite the significant associated costs. In shorter tunnels, however, natural ventilation may be sufficient to comply with safety regulations. Accordingly, the analysis of natural fire smoke flow is relevant for tunnels shorter than 1000 m. This paper presents a computational investigation of the influence of the tunnel slope on the contamination of the cold lower layer with smoke and discusses how it impairs the user’s egress. Large-eddy simulations of the smoke propagation show three different regimes, namely, a quasi-horizontal tunnel behavior for a slope of 0.5%, a transitional behavior for slopes in the range of 1% to 5% and a quasi-forced ventilation behavior for a slope of 7%. The computational results are compared with the application of 1D equations to predict the upper layer temperature, the average mass flow rate, the upper layer mass flow rate, the upper layer velocity and the lower layer velocity. The distance from the fire to the location where the lower layer contamination with smoke starts is accurately predicted by the one-dimensional model for slopes of 2% and 3.5%. However, in the case of lower or higher slopes, the one-dimensional model performs poorly and needs further improvement.

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“…The smoke temperature distribution beneath the ceiling of the inclined tunnel was investigated by conducting full-scale fire experiments and small-scale fire experiments. [10][11][12] Results showed that the smoke temperature decayed exponentially along the tunnel ceiling and decreased faster with a larger slope under natural ventilation. Scholars have conducted studies about the smoke back-layering length and the critical longitudinal velocity in inclined tunnel fires.…”

Section: Introductionmentioning

confidence: 99%

A simplified calculation method on the smoke back-layering length and inlet air velocity in a tilted tunnel fire without shaft

et al. 2022

Indoor and Built Environment

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In a tilted tunnel fire, the inlet air velocity caused by the stack effect at the entrance of the tunnel would be beneficial to smoke control whether the longitudinal ventilation system is used or not. This paper conducted the simulation to investigate the smoke spread behaviours caused by fires in tilted tunnels with natural ventilation. The expression of the smoke back-layering length and the inlet air velocity induced by fires were deduced in the tilted tunnel fire scenarios by the method of dimensional analysis. The effect of various tunnel slopes (5–15%) on the smoke behaviours characteristics and the inlet air velocity were specifically considered. The proposed correlation reveals that the dimensionless back-layering length is independent of the heat release rate (HRR) and its relationship with the tunnel slope is proportional to −1.96 power. The established equation reveals that the dimensionless inlet air velocity is proportional to 0.31 power of the dimensionless HRR and it increases exponentially with the tunnel slope. This research on this topic may contribute to optimize the application of natural ventilation systems or mechanical ventilation in tilted tunnels.

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A study on ceiling jet characteristics in an inclined tunnel

Cited by 50 publications

References 22 publications

Experimental study and analysis of radiation heat fluxes received by a floor beneath an inclined ceiling

Experimental study and analysis of radiation heat fluxes received by a floor beneath an inclined ceiling

The Contamination of the Lower Layer in Sloped Tunnel Fires

A simplified calculation method on the smoke back-layering length and inlet air velocity in a tilted tunnel fire without shaft

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