Experimental study of upward flame spread over discrete thin fuels

Cui, Wohan; Liao, Ya-Ting T.

doi:10.1016/j.firesaf.2019.102907

Cited by 22 publications

(13 citation statements)

References 18 publications

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“…When the flame reaches the top of PMMA array, it is shown in a wavy form under the influence of air gaps. The flame is thin at air gaps, while it is thick on the surface of PMMA, which is similar to the experimental phenomena in the works of Park [ 26 ] and Cui et al [ 27 ]. The continuous flame is significantly brighter than the discrete flame.…”

Section: Resultssupporting

confidence: 87%

“…Park and Liao [ 26 ] studied the influence of air gap on the vertical flame spread of thermally thin materials through numerical simulation and small-scale experiments, finding two aspects of the influence: one is the jumping phenomenon at the flame bottom and flame front, and the other is that the air gap makes upward flames closer to the fuel surface, leading to stronger flame heat flow received by the fuel surface. Cui et al [ 27 ] further studied the influence of air gaps with different lengths on the vertical flame spread over thin filter papers, and found that as the air gap gets larger, the flame spread rate and mass loss rate increases first and then decreases. Miller et al [ 6 ] studied the upward flame spread characteristics of PMMA when noncombustible isolation strips are arranged at the same spacing, and indicated that the flame spread rate increases first and then decreases as fuel coverage (ƒ) decreases, and reaches its maximum when ƒ = 0.64.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamic and Kinetic Characteristics of Combustion of Discrete Polymethyl Methacrylate Plates with Different Spacings in Concave Building Facades

Peng

Cai

et al. 2021

Polymers

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Polymethyl methacrylate plates are widely applied to buildings, producing significant fire hazards. It lacks a theoretical basis for the fire risk assessment of polymethyl methacrylate in concave building facades. Therefore, experimental methods are used to investigate combustion characteristics of discrete polymethyl methacrylate plates in a concave building facade. Influences of fuel coverage and structure factor are investigated, which is scant in previous works. When structure factor is invariable, average flame height increases first and then decreases as fuel coverage increases, and the turning point is between 0.64 and 0.76. In total, three different patterns of pyrolysis front propagation are first observed for different fuel coverages. Flame spread rate first increases and then decreases as fuel coverage rises, and the turning point is also between 0.64 and 0.76. When fuel coverage is invariable, the flame spread rate first increases and then decreases with increasing structure factor, and the turning point is 1.2. A model for predicting the flame spread rate of discrete polymethyl methacrylate is also developed. The predicted values are consistent with experimental results. Fuel spread rate of discrete polymethyl methacrylate rises as the fuel coverage increases. The above results are beneficial for thermal hazard evaluation and fire safety design of polymethyl methacrylate used in buildings.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Thermodynamic and Kinetic Characteristics of Combustion of Discrete Polymethyl Methacrylate Plates with Different Spacings in Concave Building Facades

Peng

Cai

et al. 2021

Polymers

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“…The wire is wrapped around an ignition paper strip (0.7 cm tall, 4.5 cm wide) mounted 3.5 cm beneath the first fuel strip. 27 Two DSLR cameras (Canon T3i, 1920 × 1080 pixel resolution at 30 frames per second rate) are used to record the burning process from the front and edge views. Both cameras were manually set to the fixed parameters (aperture: 4.5, shutter speed: 1/60, ISO: 1600, manual white balance) to facilitate image comparisons between different tests and between different video frames in the same test.…”

Section: Methodsmentioning

confidence: 99%

“…This is because the flame base needs to jump across the gaps to reach the downstream fuels. 26,27 In Figure 4(c), the flame base location is adjusted by subtracting the total length of the discrete gaps traversed by the flame base. In this work, flame front spread rate ( V f ) , flame base spread rate ( V b ) , and fuel burnout rate ( V b * ) are deduced by applying linear fitting to the flame front ( x f ) , flame base ( x b ) , and adjusted flame base ( x b * ) locations, respectively (see dashed lines in Figures 4(a) to (c)).…”

Section: Transient Flame Spread Over Continuous and Discrete Fuelsmentioning

confidence: 99%

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Upward flame spread over discrete thin solids separated by heat-absorbing inert materials

Cui

Sharma

Liao

2023

Journal of Fire Sciences

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Flame spread over discrete solid fuels has been of key research interest in the past few decades. Most studies considered an array of discrete fuels separated by air gaps or heat-insulating inert materials. The effects of heat loss due to the discrete configuration are not well understood. The present study aims to bridge this knowledge gap. A series of experiments are performed using a vertical array of thin discrete fuels separated by heat-absorbing inert materials of different thicknesses. For comparisons, experiments are also performed using discrete fuels separated by air gaps and using continuous fuel. The flame base spread rate is found to be generally higher in discrete fuel than in continuous fuel configurations, due to a reduced fuel load per unit length. It is also found that the air and inert gaps have opposite effects on the solid burning rates. The air gaps break the no-slip boundary, allowing the laterally entrained buoyancy flow (normal to the sample surface) to push the flame closer to the samples. This leads to an enhanced heat flux on the sample surface and an increased solid burning rate. On the other hand, the inert materials retain the flow boundary profile and act as a heat sink during flame spread, thereby reducing the solid burning rate. As the inert thickness increases, flame spread rate and solid burning rate decrease. Based on these observations, an existing model for flame spread rate is updated by incorporating the heat-absorbing effects of the gaps. The correlation is validated using the experimental data.

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