Width effects on the early stage of upward flame spread over PMMA slabs: Experimental observations

Pizzo, Yannick; Consalvi, Jean-Louis; Querre, P.; Coutin, M.; Porterie, B.

doi:10.1016/j.firesaf.2008.09.003

Cited by 81 publications

(49 citation statements)

References 21 publications

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“…Typical vertical fires do not spread in the presence of any sort of well-defined sidewall. Additionally, Pizzo demonstrated that, for flames of comparable proportion to those studied here, both flame height and spread rate were independent of width for flames wider than 10 cm [27].…”

Section: Previous Research On Upward Flame Spreadsupporting

confidence: 57%

“…Drysdale and MacMillan studied effects of fuel orientation on the flame spread rate, and found substantially higher velocities as the angle of orientation approached the vertical [23]. 10 cm is independent of width [27]. It was confirmed that as the width increases, a smaller fraction of the fire will be influenced by edge effects, notably the lateral diffusion of air in the absence of sidewalls.…”

Section: Previous Research On Upward Flame Spreadmentioning

confidence: 90%

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Upward flame spread over discrete fuels

Miller

Gollner

2015

Fire Safety Journal

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Upward flame spread over discrete fuels has been analyzed through experimental research on vertical arrays of alternating lengths of PMMA and insulation. By manipulating the lengths of the PMMA fuel and the insulation, several important trends related to flame spread were identified and assessed.The peak flame spread rate for arrays with 4 cm lengths of PMMA occurred at a fuel percentage of 67%; for arrays with 8 cm PMMA, a peak flame spread rate occurred at fuel percentages of 67%, 80%, and 89%. It has been hypothesized that increased air entrainment at these fuel percentages maximizes the flame spread rate.Based on observed trends, this study proposed a method for approximation of the fuel spread rate at various fuel percentages. Given reasonable estimates for the homogeneous flame spread rate and the lowest fuel percentage that sustains spread, an estimation for intermediate spread rate values is feasible.

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Section: Previous Research On Upward Flame Spreadsupporting

confidence: 57%

Section: Previous Research On Upward Flame Spreadmentioning

confidence: 90%

Upward flame spread over discrete fuels

Miller

Gollner

2015

Fire Safety Journal

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“…For horizontal flame spread, Li et al [3] demonstrated that flame spread rate increased with a rise in sample width, while Mell et al [4] concluded that the reverse is true. Rangwala et al [5] and Pizzo et al [6] attributed width effects to heat diffusion by sample sides. However, Mell et al [4] hypothesized that these phenomena were caused by the convective heat transfer variation due to a change in width.…”

Section: Introductionmentioning

confidence: 99%

Effects of Sample Width and Sidewalls on Downward Flame Spread over XPS Slabs

An¹,

Xiao²,

Sun³

et al. 2014

Fire Saf. Sci.

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To study the effects of sample width and sidewalls on downward flame spread over extruded polystyrene (XPS) slabs, a series of laboratory-scale experiments were conducted. Flame shape, flame spread rate, mass loss rate and temperature were recorded. For XPS without sidewalls, the average maximum flame height (H) and average flame area per unit of width (A/w) rise linearly with an increase in sample width (w) and mass loss rate per unit of width. When sidewalls are absent, flame spread rate first drops and then rises with an increase in width. This trend is determined by gas-phase heat transfer. When sidewalls are present, flame spread rate increases with a rise in width, and solid-phase heat conduction determines the trend. Sidewall effects are comprised of four aspects: oxygen concentration near the sidewalls and gypsum board is low, which leads to reduced flame heat flux; upward and front air flow is intensified; the flame is stretched, and the surface flame is weakened; and molten XPS mass decreases. For narrow samples, H and A/w with sidewalls are higher than those without sidewalls, while the reverse was observed in wider samples. The mass loss rate, preheating length and average flame spread rate with sidewalls are smaller than those obtained without sidewalls. Flame spread acceleration with sidewalls occurs at a broader width than that without sidewalls. The experimental results agree well with the theoretical analysis.

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“…In contrast, in a radiative dominant regime, this rate should rise when sample width is large. For upward flame spread with finite sample width, flame radiation is dominant and the rate of spread increases with sample width [3][4][5]. However, for horizontal flame spread, opinions as to width effects on spread rate are wide and no consensus has been reached.…”

mentioning

confidence: 99%

“…sample width effects) on surface flame spread need to be explored. Recent research [3][4][5][6] has reported that sample width below a certain threshold value has an important role in flame spread. For surface flame spread, the spread rate is influenced by flame convection and radiation.…”

mentioning

confidence: 99%

Effects of sample width on flame spread over horizontal charring solid surfaces on a plateau

Zhang

Huang

et al. 2011

Chin. Sci. Bull.

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Experiments were conducted on the Tibetan Plateau to investigate the effects of sample width (W) on flame spread over horizontal charring solid surfaces. The results show that the rate of spread is influenced by the combined effects of convection heat transfer and flame radiation. Moreover, two different regimes depending on sample width were found in flame spread behavior. The rate of spread decreased with width in the convective regime (W≤3 cm) but increased in the radiative regime (W>3 cm). Similar results were observed in comparative experiments conducted on a plain in Hefei, with the rate of spread reaching its minimum value at W=4 cm rather than 3 cm. Flame spread over solid surfaces is a common phenomenon in fire accidents. Studying flame spread behavior is useful in predicting fire growth. Many studies have been conducted to explore the characteristics of flame spread. However, most research on flame spread over wood surfaces has been conducted on plains; few studies on the characteristics of flame spread on high plateaus have been reported, especially at altitudes over 3000 m. Recent research indicated that ignition times of wood at altitude might be shorter [1] than at sea level and the combustion temperature of the flame might be higher [2], which means that fire accidents on plateaus might be potentially more hazardous. Conducting further research on the characteristics of flame spread over wood surfaces on high plateaus could provide basic data and ultimately benefit fire control and prevention at higher altitudes. Much of the surface flame spread experiments were conducted on a laboratory scale owing to limitations in experimental conditions. To apply these small-scale experimental results to real large-scale fire situations, scale effects *Corresponding author (email: sunjh@ustc.edu.cn) (e.g. sample width effects) on surface flame spread need to be explored. Recent research [3][4][5][6] has reported that sample width below a certain threshold value has an important role in flame spread. For surface flame spread, the spread rate is influenced by flame convection and radiation. The convective heat transfer decreases with width while radiation increases with scale. Therefore, when the sample is narrow, convective effects are dominant and flame spread rate should drop. In contrast, in a radiative dominant regime, this rate should rise when sample width is large. For upward flame spread with finite sample width, flame radiation is dominant and the rate of spread increases with sample width [3][4][5]. However, for horizontal flame spread, opinions as to width effects on spread rate are wide and no consensus has been reached. Flame spread rates over cellulosic samples at small widths of 2−5 cm were studied in numerical simulations by Mell and Kashiwagi [7], and they found that rates of spread decreased with width. Li et al.[2] performed flame spread experiments over wood surfaces with a larger width range of 2−11 cm, with a width interval of 3 cm, and found the rate of spread increased with sample width....

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Width effects on the early stage of upward flame spread over PMMA slabs: Experimental observations

Cited by 81 publications

References 21 publications

Upward flame spread over discrete fuels

Upward flame spread over discrete fuels

Effects of Sample Width and Sidewalls on Downward Flame Spread over XPS Slabs

Effects of sample width on flame spread over horizontal charring solid surfaces on a plateau

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