Dependence of flame height of internal fire whirl in a vertical shaft on fuel burning rate in pool fire

The fire whirl generated by burning a pool fire in a vertical shaft with a single corner gap of appropriate width was studied using a high-speed camera. A 7-cm diameter pool propanol fire with heat release rate 1.6 kW in free space was burnt inside a 145-cm tall vertical shaft model with gap widths lying between 2 cm and 16 cm. The flame height was between 0.25 m and 0.85 m for different gap widths. Photographs taken using a high-speed camera at critical times of swirling motion development were used to compare with those taken using a normal camera. From the experimental observations on flame swirling by a high-speed camera, stages for generating the fire whirl were identified much more accurately. Two flame vortex tubes moving over the horizontal burning surface of the liquid pool were observed. Based on these observations a set of more detailed schematic diagrams on the swirling motion was constructed. From the observed flame heights under different gap widths and using three assumptions on the variation of air entrainment velocity with height, an empirical expression relating the burning rate with flame height and the corner gap width was derived from the observation with high-speed camera. The correlation expression of the burning rate of the pool fire obtained would be useful in fire safety design in vertical shafts of tall buildings.

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A study of correlation between flame height and gap width of an internal fire whirl in a vertical shaft with a single corner gap

Indoor and Built Environment ◽

10.1177/1420326x17729742 ◽

2017 ◽

Vol 28 (1) ◽

pp. 34-45 ◽

Cited By ~ 1

Author(s):

G. W. Zou ◽

H. Y. Hung ◽

W. K. Chow

Keyword(s):

Experimental Data ◽

Fire Safety ◽

Air Entrainment ◽

Pool Fire ◽

Flame Height ◽

Vertical Shaft ◽

Entrainment Velocity ◽

Fire Safety Design ◽

Fire Whirl ◽

Gap Width

An internal fire whirl can be generated by a pool fire burning in a vertical shaft with a single corner gap of appropriate width. In an internal fire whirl, the flame height is an important characteristic in terms of fire safety. In this paper, a correlation expression of flame height with the width of a single corner gap was studied using reported experimental data in a 9-m tall vertical shaft model. A pool of gasoline fuel was burnt inside the shaft model to study the characteristics of flame swirling. An internal fire whirl was generated for gap widths lying between 0.11 m and 0.66 m, when the pool fire was 0.46 m diameter. The flame height was between 2.5 m and 3.2 m. From the experimental observations on flame swirling for different gap widths, coupled with three assumptions on variation of air entrainment velocity with height, an expression relating the flame height and the corner gap width was derived for the internal fire whirl using a set of compiled experimental data. The correlation expression obtained would be useful for fire safety design in vertical shafts.

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Some Experimental Results on Internal Fire Whirls in a Vertical Shaft

Volume 8A: Heat Transfer and Thermal Engineering ◽

10.1115/imece2013-62148 ◽

2013 ◽

Author(s):

Y. Gao ◽

G. W. Zou ◽

S. S. Li ◽

W. K. Chow

Keyword(s):

Full Scale ◽

Pool Fire ◽

Experimental Results ◽

Vertical Shaft ◽

Remote Site ◽

Scale Modeling ◽

Key Factor ◽

Fire Whirl ◽

Real Scale

Earlier studies on burning a pool fire in a vertical shaft model indicated that appropriate sidewall ventilation provision is a key factor for the onset of an internal fire whirl. Experiments on burning a pool fire inside a real-scale shaft model of 9 m tall were performed to further investigate the swirling motion. The full-scale modeling burning tests were carried out at a remote site in China. Four different ventilation openings were arranged. Results of onsetting of internal fire whirls for the four tests will be reported.

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Internal Fire Whirls Induced by Pool Fire in a Vertical Shaft

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44477 ◽

2011 ◽

Cited By ~ 1

Author(s):

Yan Huo ◽

W. K. Chow ◽

Ye Gao

Keyword(s):

Flow Field ◽

Numerical Simulations ◽

Air Flow ◽

Pool Fire ◽

Vertical Shaft ◽

Pool Fires ◽

Key Factor ◽

Fire Whirl ◽

Gap Width

Internal fire whirls induced by a pool fire in a square vertical shaft were studied by experiments and numerical simulations. The burning behaviour of two pool fires in the vertical shaft and in open air was compared. The gap width of the rig is a key factor in onsetting fire whirls. Air flow field in the vertical square shaft of different gap widths were studied experimentally with nine tests. A fire whirl would not be onsetted when the gap is too narrow nor too wide. Whirling flame is not clearly observed near to the bottom of the vertical shaft when the gap width was small.

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A study on relationship between burning rate and flame height of internal fire whirls in a vertical shaft model

Journal of Fire Sciences ◽

10.1177/0734904113496535 ◽

2013 ◽

Vol 32 (1) ◽

pp. 72-83 ◽

Cited By ~ 4

Author(s):

Wan K. Chow

Keyword(s):

Burning Rate ◽

Flame Height ◽

Vertical Shaft

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Blind Simulation of Periodic Pressure and Burning Rate Instabilities in the Event of a Pool Fire in a Confined and Mechanically Ventilated Compartment

Combustion Science and Technology ◽

10.1080/00102202.2016.1139365 ◽

2016 ◽

Vol 188 (4-5) ◽

pp. 504-515 ◽

Cited By ~ 6

Author(s):

T. Beji ◽

B. Merci

Keyword(s):

Burning Rate ◽

Pool Fire ◽

Mechanically Ventilated ◽

Periodic Pressure

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Thermal and Fluid Dynamic Structures of a Laboratory-Scale Fixed-Frame Fire-Whirl

10.1115/imece2001/htd-24246 ◽

2001 ◽

Author(s):

Mohamed I. Hassan ◽

A. Helali ◽

Kozo Saito

Keyword(s):

Heat Flux ◽

Fluid Dynamic ◽

Azimuthal Velocity ◽

Video Camera ◽

Liquid Pool ◽

Flame Height ◽

Buoyancy Flow ◽

Image Velocimetry ◽

Fire Whirl ◽

Dynamic Structures

Abstract Fire whirl is one of the most destructive phenomena in mass fires. To study thermal and fluid dynamic structures of a fire whirl in a laboratory, a fire whirl generator consisting of two vertically oriented split-cylinders were placed in an asymmetric position to form a compartment leaving two open slits in each end. A 5-cm diameter liquid pool fire was placed at the center of the compartment floor, the fire generated buoyancy flow moved upwardly, and fresh air entered to the compartment creating swirl motion. The visible flame height of the generated fire whirl was measured by a video camera, 2-D azimuthal velocity profiles at several different heights by particle image velocimetry (PIV), and the average heat flux input to the fuel surface by a Gardon gauge type heat flux meter.

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Modeling on n-Heptane Pool Fire Behavior in an Altitude Chamber

Volume 8A: Heat Transfer and Thermal Engineering ◽

10.1115/imece2013-62367 ◽

2013 ◽

Author(s):

Quanyi Liu ◽

Wei Yao ◽

Jiusheng Yin ◽

Rui Yang ◽

Hui Zhang

Keyword(s):

High Altitude ◽

Burning Rate ◽

Pressure Effect ◽

Fire Behavior ◽

Low Pressure ◽

Pool Fire ◽

Low Oxygen ◽

Fire Plume ◽

Plume Temperature ◽

Modeling Data

Airplane as one of the important transport vehicles in our life, its safety problem related to in-flight fire has attracted a wide-spread attention. The combustion behavior of the cabin fire in flight shows some special characteristics because of the high-altitude environment with low-pressure and low oxygen concentration. A low-pressure chamber of size 2 m×3 m×2 m has been built to simulate high-altitude environments, where multiple static pressures for pool fire tests can be configured in the range between standard atmospheric pressure 101.3KPa and 30KPa. Two different sizes of pool fires were tested. Then corresponding modeling were conducted by a LES code FDS V5.5 to examine the mechanism of pressure effect on the n-Heptane pool fire behavior. The burning of liquid fuel was modeled by a Clausius-Clapeyron relation based liquid pyrolysis model. The modeling data was validated against the experimental measurements. The mass burning rate of free-burning pool fire decreases with the decreasing of pressure, which was observed from the modeling to be due to the reduction of flame heat feedback to the fuel surface. Under low pressure, the fire plume temperature increases for the same burning rate. The mechanism of pressure effect on fire behavior was analyzed based on the modeling data.

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Influence of Eddy-Generation Mechanism on the Characteristic of On-Source Fire Whirl

Applied Sciences ◽

10.3390/app9193989 ◽

2019 ◽

Vol 9 (19) ◽

pp. 3989 ◽

Cited By ~ 2

Author(s):

Cheng Wang ◽

Anthony Chun Yin Yuen ◽

Qing Nian Chan ◽

Timothy Bo Yuan Chen ◽

Qian Chen ◽

...

Keyword(s):

Flame Structure ◽

Flame Temperature ◽

Combustion Process ◽

Flame Height ◽

Reacting Flow ◽

Detailed Chemistry ◽

Eddy Generation ◽

Fire Whirl ◽

Generation Mechanisms ◽

The Impact

This paper numerically examines the characterisation of fire whirl formulated under various entrainment conditions in an enclosed configuration. The numerical framework, integrating large eddy simulation and detailed chemistry, is constructed to assess the whirling flame behaviours. The proposed model constraints the convoluted coupling effects, e.g., the interrelation between combustion, flow dynamics and radiative feedback, thus focuses on assessing the impact on flame structure and flow behaviour solely attribute to the eddy-generation mechanisms. The baseline model is validated well against the experimental data. The data of the comparison case, with the introduction of additional flow channelling slit, is subsequently generated for comparison. The result suggests that, with the intensified circulation, the generated fire whirl increased by 9.42 % in peak flame temperature, 84.38 % in visible flame height, 6.81 % in axial velocity, and 46.14 % in velocity dominant region. The fire whirl core radius of the comparison case was well constrained within all monitored heights, whereas that of the baseline tended to disperse at 0.5 m height-above-burner. This study demonstrates that amplified eddy generation via the additional flow channelling slit enhances the mixing of all reactant species and intensifies the combustion process, resulting in an elongated and converging whirling core of the reacting flow.

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