Internal Fire Whirls in a Vertical Shaft

Chow, Wan Ki; He, Zhi Cheng; Ye, Gao

doi:10.1177/0734904110378974

Cited by 27 publications

(42 citation statements)

References 15 publications

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“…This suggests that, for small fire whirls, the flame height is circulation controlled, whereas for large fire whirls other parameters such as the burning rate and the buoyancy are also important. Chow et al (2010) also established a positive correlation between the fire whirl height and the product of the dimensionless fire powerQ * and pool diameter D 0 : H = 3.59Q * 2/5 D 0 . Byram & Martin (1962) and Lei et al (2011) have argued that the flame radius in the continuous flame region is nearly equal to that of the vortex core above the radial boundary layer (Byram & Martin 1962;Lei et al 2011).…”

Section: Heightmentioning

confidence: 99%

Fire Whirls

Tohidi

Gollner

Xiao

2018

Annu. Rev. Fluid Mech.

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Fire whirls present a powerful intensification of combustion, long studied in the fire research community because of the dangers they present during large urban and wildland fires. However, their destructive power has hidden many features of their formation, growth, and propagation. Therefore, most of what is known about fire whirls comes from scale modeling experiments in the laboratory. Both the methods of formation, which are dominated by wind and geometry, and the inner structure of the whirl, including velocity and temperature fields, have been studied at this scale. Quasi-steady fire whirls directly over a fuel source form the bulk of current experimental knowledge, although many other cases exist in nature. The structure of fire whirls has yet to be reliably measured at large scales; however, scaling laws have been relatively successful in modeling the conditions for formation from small to large scales. This review surveys the state of knowledge concerning the fluid dynamics of fire whirls, including the conditions for their formation, their structure, and the mechanisms that control their unique state. We highlight recent discoveries and survey potential avenues for future research, including using the properties of fire whirls for efficient remediation and energy generation.

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Section: Heightmentioning

confidence: 99%

Fire Whirls

Tohidi

Gollner

Xiao

2018

Annu. Rev. Fluid Mech.

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“…A fire whirl can be generated by burning a pool fire in a vertical shaft model of appropriate gap widths [11][12][13][14][15]20]. Such experiments were carried out to investigate the effect of the gap width on IFW generation.…”

Section: Experimental Studiesmentioning

confidence: 99%

“…An IFW has a fixed physical fire size, and does not spread over the fuel surface as in open space. An IFW can be created in a vertical shaft in tall buildings with appropriate sidewall ventilation arrangement [11][12][13][14][15]. This is hazardous to green buildings with tall shafts or good thermal insulation [16][17][18] and studied as a long-term project.…”

Section: Introductionmentioning

confidence: 99%

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Observation on a fire whirl in a vertical shaft using high-speed camera and associated correlation derived

et al. 2021

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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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“…Recently, a series of small to medium-scale vertical shaft fire whirl experiments has been carried out by Chow, Zou and co-workers [5][6][7]. It was demonstrated that the generation of fire whirl could be sub-divided into four stages including (i) initial ignition stage where the flame height is relatively low; (ii) flame rising-up stage where the flame height increase gradually to reach its upcoming state; (iii) stable whirling stage where the flame height is considered to be at its maximum height; (iv) decaying stage where the whirling motion stops and the fire gradually extinguishes.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study on Small-Scale Fire Whirl using Large Eddy Simulation

Yuen¹,

Yeoh²,

Yuen³

et al. 2016

International Conference of Fluid Flow, Heat and Mass Transfer

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-Fire whirl is a rotating fire with either a fixed or revolving flame centre-core caused by unbalanced entrainment. In general, the flame height of a fire whirl is significantly larger than that of a free standing fire. It is suggested by several studies that fire whirl is a disastrous scenario especially in urban or bush fires since it can greatly promote the fire spread and escalate the thread to human lives and species. In this paper, as a preliminary study, the fire whirl behaviour has been studied numerically using the Fire Dynamics Simulator (FDS) ver 6.1.2 which is based on the large eddy simulation (LES). It incorporates the mixture fraction based combustion model along with soot formation, the subgrid-scale (SGS) turbulence model, radiation transfer equation (RTE) model which are fully coupled and interactive. This allows the modelling of all essential chemical and physical behaviours that occur during the fire whirling processes. A small-scale vertical shaft with a base of 0.34 m × 0.35 m with a total vertical height of 1.45 m is considered. The development stages including the ignition, flame-rising and fully-developed fire whirling are modelled successfully through numerical simulations. Fairly good agreements between simulation and experimental results for temperature profiles at the centreline and corner thermocouples are achieved. However, a flame height of 0.3 m to 0.4 m is estimated in the simulation while the experimental observation is around 0.6 m. Also, the temperature is slightly over-predicted at the centre while under-predicted at the corner. These could well be due to the simplified chemistry employed in the FDS. With this preliminary numerical study, it could be logically inferred that the detailed chemical reactions scheme may be needed to capture the fundamental governing characteristics of the fire whirl in future numerical modelling studies.

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Internal Fire Whirls in a Vertical Shaft

Cited by 27 publications

References 15 publications

Fire Whirls

Fire Whirls

Observation on a fire whirl in a vertical shaft using high-speed camera and associated correlation derived

Numerical Study on Small-Scale Fire Whirl using Large Eddy Simulation

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