Effect of width and slope of large cross-section tunnel on ceiling smoke temperature under natural ventilation

ABSTRACT

When a fire occurs in a large cross-section tunnel with slope, the distribution characteristic of ceiling smoke temperature illustrates special laws under the effect of chimney effect, the thermal radiation feedback, and the air entrance limit from walls. A series of numerical simulations are conducted through FDS simulation software based on the actual size of highway tunnel. The influence of large cross-section tunnel width and slope on ceiling smoke temperature when fire occurs are discussed. The research results show that (1) as the tunnel slope increases from 5° to 20°, the distance between the maximum ceiling smoke temperature point and the fire source is 0.5 m, 1 m, 1.7 m, 2.4 m, respectively, and the distance between the ceiling impact point and the fire source is 1 m, 1.8 m, 2.3 m, 3 m, respectively. As the tunnel width increases from 10 m to 20 m, the distance between maximum ceiling smoke temperature point and fire source increases 0.9 m, 1.1 m, 1.3 m, 1.8 m, 2.5 m, and 2.6 m. (2) The prediction formula of maximum ceiling smoke temperature is modified, and a dimensionless relationship among the maximum ceiling smoke temperature and tunnel slope and tunnel width is established. (3) The formula of longitudinal ceiling smoke temperature distribution is modified, and the relationship among tunnel slope, tunnel width, tunnel height, and longitudinal ceiling smoke temperature distribution is established. The research conclusions can provide a theoretical basis for fire prevention design, smoke control and evacuation of this kind of large cross-section tunnel fire.

KEYWORDS:

• Natural ventilation
• large cross-section tunnel
• fire
• tunnel width
• tunnel slope
• ceiling smoke temperature

Acknowledgements

The research is supported by the National Natural Science Foundation of China (No. 51774067). The authors are grateful for the support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Su Liu: participation in the whole work; drafting of the article; Peihong Zhang: checked and modified this paper; Chenghao Ye: provided technical guidance. All authors have read and agreed to the published version of the manuscript.

Data availability statement

Data will be made available on request

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [51774067].

Notes on contributors

Su Liu

Su Liu, a PhD student at Northeastern University, she is mainly engaged in the field of fire safety science and technology and mechanical ventilation.

Chenghao Ye

Chenghao Ye, he is currently a doctoral candidate at Northeastern University, he is mainly engaged in the field of fire safety science and technology and thermal environment control research.

Peihong Zhang

Peihong Zhang, a professor at Northeastern University, she is mainly engaged in scientific research in the fields of fire safety science and technology, emergency evacuation, mechanical ventilation and thermal environment control for many years.