Ignition of Combustion Modified Polyurethane Foam

Putzeys, Olivier; Fernandez-Pello, Carlos; Urban, David L.

doi:10.1520/jai13558

Cited by 5 publications

(6 citation statements)

References 18 publications

(16 reference statements)

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“…In all investigated consolidated WUI fuels (Table 2), the StF transition occurred only if the smouldering sample was assisted with heat insulation, heated boundaries, and increased ambient oxygen concentration (Ortiz-Molina et al, 1979;Tse et al, 1996;Bar-Ilan et al, 2005;Putzeys et al, 2006Putzeys et al, , 2007Putzeys et al, , 2008Chang et al, 2011). However, this finding is not the case when there is a radiation exchange between smouldering char surfaces (Alexopoulos and Drysdale, 1988;Ohlemiller, 1991;Stoliarov et al, 2017).…”

Section: Role Of Oxygen Supply and Heat Transfermentioning

confidence: 93%

“…This result implies that increased oxygen diffusion penetration into smouldering fuel under increased ambient pressure leads to lower critical oxygen concentration. However, when the ambient oxygen concentration is further increased to 35-54 vol% with assistive heating (4.5-55 kW/m 2 ), the StF transition can occur in samples with characteristic lengths as small as 10-12.5 cm (Sato and Sega, 1991;Bilbao et al, 2001;Bar-Ilan et al, 2005;Putzeys et al, 2006Putzeys et al, , 2007Putzeys et al, , 2008.…”

Section: Role Of Oxygen Supply and Heat Transfermentioning

confidence: 99%

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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: Role Of Oxygen Supply and Heat Transfermentioning

confidence: 93%

Section: Role Of Oxygen Supply and Heat Transfermentioning

confidence: 99%

Review of the Transition From Smouldering to Flaming Combustion in Wildfires

et al. 2019

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“…The experimental setup is a modification of that previously used to study the spontaneous transition from smoldering to flaming [9,10,12]. It consists of a vertically oriented foam sample heated on three of its surfaces with guard heaters and with the fourth, free surface, exposed to a parallel forced oxidizer flow and radiant heat flux.…”

Section: Experimental Conceptmentioning

confidence: 99%

“…Several works have studied the spontaneous transition from smoldering to flaming, whereby the smolder reaction supplies the gaseous fuel and the heat to trigger a gas-phase ignition [8][9][10][11][12]. However, very little fundamental work has been done on the piloted ignition of the gaseous products of smoldering [13].…”

Section: Introductionmentioning

confidence: 99%

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The piloted transition to flaming in smoldering fire retarded and non‐fire retarded polyurethane foam

et al. 2008

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The piloted transition from smoldering to flaming, though a significant fire safety concern, has not been previously extensively studied. Experimental results are presented on the piloted transition from smoldering to flaming in non-fire retarded (NFR) polyurethane foam and the fire retarded polyurethane foam Pyrell ® . The samples are small blocks, vertically placed in the wall of an upward wind tunnel. The free surface is exposed to an oxidizer flow and a radiant heat flux. The smolder product gases pass upwards through a pilot. The experiments on NFR foam show that the smolder velocity and peak smolder temperature, which increase with the oxygen concentration and heat flux, are strongly correlated to the transition to flaming event, in that there are minimum values of these parameters for transition to occur. The existence of a minimum smolder velocity for ignition supports the concept of a gaseous mixture reaching a lean flammability limit as the criterion for the transition to flaming. To compensate for the solid-and gas-phase effects of the fire retardants on the piloted transition in Pyrell, it was necessary to increase the oxygen concentration and the power supplied to the smolder igniter and the pilot. The piloted transition is observed in oxygen concentrations above 17% in NFR foam, and above 23% in Pyrell. The results show that although Pyrell is less flammable than NFR foam, it is still susceptible to smoldering and the piloted transition to flaming in oxygen-enriched environments, which is of interest for special applications such as future space missions.

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