Fire properties in near field of square fire source with longitudinal ventilation in tunnels

In this study, a large compartment was used and opening shapes were changed to set fire-source conditions and then combustion tests were conducted to quantitatively measure temperature and heat flux near a façade wall. In addition, q was inferred from the relationship between z and q for the top of the opening under different fire-source conditions and for various opening shapes so that q could be used as a reference index.

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Review of Research on critical velocity in tunnel fire

E3S Web of Conferences ◽

10.1051/e3sconf/20197902001 ◽

2019 ◽

Vol 79 ◽

pp. 02001 ◽

Cited By ~ 1

Author(s):

Gui-hong Pei ◽

Qiu-yi Zhang

Keyword(s):

Influencing Factors ◽

Critical Velocity ◽

Release Rate ◽

Fire Spread ◽

Fire Control ◽

Fire Source ◽

Tunnel Fire ◽

Longitudinal Ventilation ◽

Tunnel Section ◽

Ventilation Velocity

The critical velocity is the key for tunnel fire control. If the longitudinal ventilation velocity is greater than the critical velocity when the fire occurs, the upstream of the fire source is smokeless, and the smoke will flow to the downstream of the fire source, which can effectively control the fire spread and provide valuable time for personnel to escape and fire fighting. The researches of domestic and foreign scholars are used to investigate the influencing factors of critical velocity. the results show that the main influencing factors of critical velocity are fire heat release rate, tunnel section geometry, obstacle and slope in tunnel, etc. In this paper, the influencing factors are summarized, and some problems that need to be studied in tunnel fire are put forward.

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Influence of aspect ratio of tunnel on smoke temperature distribution under ceiling in near field of fire source

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2016.06.086 ◽

2016 ◽

Vol 106 ◽

pp. 1094-1102 ◽

Cited By ~ 43

Author(s):

Jie Ji ◽

Yubo Bi ◽

Kondapalli Venkatasubbaiah ◽

Kaiyuan Li

Keyword(s):

Temperature Distribution ◽

Aspect Ratio ◽

Near Field ◽

Fire Source

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Near-field scanning optical microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100144644 ◽

1986 ◽

Vol 44 ◽

pp. 642-643

Author(s):

E. Betzig ◽

A. Harootunian ◽

M. Isaacson ◽

A. Lewis

Keyword(s):

Near Field ◽

Optical Microscope ◽

Visible Radiation ◽

Field Methods ◽

Optical Elements ◽

Optical Region ◽

Order Of Magnitude ◽

Nondestructive Imaging ◽

Scanning Optical Microscopy ◽

Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

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