Transition from smoldering to flaming fire in short cotton samples with asymmetrical boundary conditions

Hagen, Bjarne Christian; Frette, Vidar; Kleppe, Gisle; Arntzen, Bjørn J.

doi:10.1016/j.firesaf.2014.11.004

Cited by 25 publications

(10 citation statements)

References 12 publications

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“…Once the oxygen concentration increased and mixed with the pyrolyzate gases bringin the mixture to within the flammability limits, StF transition occurred (t 5 in Figure 7B). This mechanism is consistent with the smouldering of cotton under asymmetric boundary conditions (Hagen et al, 2015). The asymmetric boundary condition was when one face of the cotton sample was closed by a concrete wall.…”

Section: Secondary Char Oxidationsupporting

confidence: 81%

Review of the Transition From Smouldering to Flaming Combustion in Wildfires

et al. 2019

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Wildfires are uncontrolled combustion events occurring in the natural environment (forest, grassland, or peatland). The frequency and size of these fires are expected to increase globally due to changes in climate, land use, and population movements, posing a significant threat to people, property, resources, and the environment. Wildfires can be broadly divided into two types: smouldering (heterogeneous combustion) and flaming (homogeneous combustion). Both are important in wildfires, and despite being fundamentally different, one can lead to the other. The smouldering-to-flaming (StF) transition is a quick initiation of homogeneous gas-phase ignition preceded by smouldering combustion, and is considered a threat because the following sudden increase in spread rate, power, and hazard. StF transition needs sufficient oxygen supply, heat generation, and pyrolysis gases. The unpredictable nature of the StF transition, both temporally and spatially, poses a challenge in wildfire prevention and mitigation. For example, a flaming fire may rekindle through the StF transition of an undetected smouldering fire or glowing embers. The current understanding of the mechanisms leading to the transition is poor and mostly limited to experiments with samples smaller than 1.2 m. Broadly, the literature has identified the two variables that govern this transition, i.e., oxygen supply and heat flux. Wind has competing effects by increasing the oxygen supply, but simultaneously increasing cooling. The permeability of a fuel and its ability to remain consolidated during burning has also been found to influence the transition. Permeability controls oxygen penetration into the fuel, and consolidation allows the formation of internal pores where StF can take place. Considering the high complexity of the StF transition problem, more studies are needed on different types of fuel, especially on wildland fuels because most studied materials are synthetic polymers. This paper synthesises the research, presents the various StF transition characteristics already in the literature, and identifies specific topics in need of further research.

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Section: Secondary Char Oxidationsupporting

confidence: 81%

Review of the Transition From Smouldering to Flaming Combustion in Wildfires

et al. 2019

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“…The strategy commonly used to analyse both flaming and smouldering combustion combines small-scale thermal analysis such as Microscale combustion calorimetry (PCFC), Thermogramivetric Analysis (TGA) and/or Differential Scanning Calorimetry (DSC) with fire reaction tests. Several medium-scale devises have been proposed by different authors [Ohlemiller 1990;Hagen 2011;Hagen 2015] to analyse the kinetics of smouldering processes.…”

Section: Fire Reactionmentioning

confidence: 99%

Improvement of fire reaction and mould growth resistance of a new bio-based thermal insulation material

Palumbo

Palacio

Navarro

et al. 2017

Construction and Building Materials

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In the present paper, the performance of an innovative thermal insulation rigid board is evaluated in terms of fire behaviour and fungal resistance. The board is based on vegetal pith and a natural gum (corn pith and sodium alginate) and it is completely compostable. This new composite was developed in previous work. Here boric acid, aluminium hydroxide and ammonium polyphosphate are used as fire retardants and montan wax, acetic acid and lactic acid are used as water repellent and fungicides respectively. Interactions between these different treatments is investigated. Both flaming and smouldering combustion processes of the different formulations are evaluated by small-scale techniques which include pyrolysis microcalorimetry and thermogravimetric analysis. A medium-scale device is also designed in order to study the impact of the different additives to the smouldering kinetics. Fire behaviour tests show that good improvement is obtained, both in flaming and smouldering combustion when boric acid is added. Although smouldering is not avoided in any case, the addition of 8% of boric acid or aluminium hydroxide slows down the speed of combustion propagation. The effect of the different additives on the moisture content and mould growth at 97% RH and 27ºC is analysed. Under such severe conditions none of the additives is able to prevent mould growth, with the exception of boric acid. None or marginal mould growth was observed on samples containing 8% of boric acid although moisture content was higher than the other cases.

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“…Whether a fire in a pile of material will develop as a smoldering fire or transit to flaming depends on different factors. For instance, increased levels of oxygen or airflow can strongly induce the transition to flaming, caused by a spontaneous gas‐phase ignition or induced by glowing embers . Transition from smoldering to flaming fire has previously been only sporadically reported, but has more recently been investigated more systematically …”

Section: Introductionmentioning

confidence: 99%

Effect of particle granularity on smoldering fire in wood chips made from wood waste: An experimental study

et al. 2020

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Fires in wood waste storages cause financial losses, are difficult to extinguish, and emit large amounts of fire effluents. The mechanisms related to fires in wood chip piles are not well elucidated. To find suitable preventive measures for handling such fires in wood waste, a better understanding of the physical properties of wood waste is needed. The present study investigates how granularity affects mechanisms of smoldering fire and transition to flaming in wood chip piles. Eighteen experiments with samples inside a top-ventilated, vertical cylinder were conducted. Heating from underneath the cylinder induced auto-ignition and smoldering fire, and temperatures and mass loss of the sample were measured. The results showed that granularity significantly affects the smoldering fire dynamics. Material containing larger wood chips (length 4-100 mm) demonstrated more irregular temperature development, higher temperatures, faster combustion, and higher mass losses than material of smaller wood chips (length <4 mm). The larger wood chips also underwent transition to flaming fires. Flaming fires were not observed for small wood chips, which instead demonstrated prolonged and steady smoldering propagation. The differences are assumed to be partly due to the different bulk densities of the samples of large and small wood chips affecting the ventilation conditions. Increased knowledge about these combustion processes and transition to flaming is vital to develop risk-reducing measures when storing wood chips made from wood waste in piles.

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Transition from smoldering to flaming fire in short cotton samples with asymmetrical boundary conditions

Cited by 25 publications

References 12 publications

Review of the Transition From Smouldering to Flaming Combustion in Wildfires

Review of the Transition From Smouldering to Flaming Combustion in Wildfires

Improvement of fire reaction and mould growth resistance of a new bio-based thermal insulation material

Effect of particle granularity on smoldering fire in wood chips made from wood waste: An experimental study

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