Flame heat fluxes and correlations of upward flame spread along vertical cylinders in various oxygen environments
01 Jan 2000-Vol. 28, Iss: 2, pp 2899-2904
TL;DR: In this paper, the authors verify theoretical dimensionless correlations for upward fire spread and determine heat fluxes on a vertical cylinder burning in various oxygen environments, using a flame spread theory, developed and verified for single-wall fires.
Abstract: The objectives of this work are to verify theoretical dimensionless correlations for upward fire spread and determine heat fluxes on a vertical cylinder burning in various oxygen environments. A flame spread theory, developed and verified for single-wall fires, provides (1) a relation between normalized pyrolysis front and normalized time starting from the beginning of the fire spread process and (2) a relation between flame height and pyrolysis length. These relations are used to analyze experimental upward fire spread data on clear poly(methyl methacrylate) (PMMA) cylinders. Experiments, reported elsewhere, were run in a flammability apparatus under well-ventilated conditions for fire spreading along clear PMMA vertical cylinders 0.025 m in diameter and 0.61 m high at three mass oxygen concentrations of supply air, 0.233, 0.279, and 0.446. The pyrolysis front location and flame heights were measured as function of time. Flame heat fluxes to the surface were not measured in these tests. By comparing the experimental results with the theoretical predictions, the theoretical scaling correlations are verified, and the flame heat fluxes to the cylinder surface are deduced for various oxygen concentrations.
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TL;DR: In this article, the authors review the recent understandings of the fundamental combustion processes in wire fire over the last three decades and highlight the complex role of the metallic core in the ignition, flame spread, burning, and extinction of wire fire.
Abstract: Electrical wires and cables have been identified as a potential source of fire in residential buildings, nuclear power plants, aircraft, and spacecraft. This work reviews the recent understandings of the fundamental combustion processes in wire fire over the last three decades. Based on experimental studies using ideal laboratory wires, physical-based theories are proposed to describe the unique wire fire phenomena. The review emphasizes the complex role of the metallic core in the ignition, flame spread, burning, and extinction of wire fire. Moreover, the influence of wire configurations and environmental conditions, such as pressure, oxygen level, and gravity, on wire-fire behaviors are discussed in detail. Finally, the challenges and problems in both the fundamental research, using laboratory wires and numerical simulations, and the applied research, using commercial cables and empirical function approaches, are thoroughly discussed to guide future wire fire research and the design of fire-safe wire and cables.
58 citations
01 Jan 2013
TL;DR: In this paper, the authors studied the heat feedback profile across 5 cm wide and 15 cm tall poly(methyl methacrylate) samples from ignition until total sample involvement as a flame spread vertically upward, and developed an analytical model that accurately predicts the measured heat flux profile along the vertical dimension of samples solely as a function of the burning rate.
Abstract: The heat feedback profile across 5 cm wide and 15 cm tall samples of poly(methyl methacrylate) was studied from ignition until total sample involvement as a flame spread vertically upward. Incident heat flux to a water-cooled gauge was measured at 1 cm intervals. At 6–15 cm above the bottom edge of the flame, the maximum heat flux value was found to be on the order of 35 kW m −2 . Lower in the sample, 2–5 cm above the flame bottom, where the flame is thinner and thus closer to the sample’s surface, the maximum heat flux is slightly higher, about 40 kW m −2 . Using these results and finely resolved measurements of sample burning rate recorded throughout the length of experiments, an analytical model that accurately predicts the measured heat flux profile along the vertical dimension of samples solely as a function of the burning rate was developed. Coupling this model with an accurate pyrolysis solver, which predicts material burning rate based on incident heat flux, is expected to enable highly accurate simulations of the flame spread dynamics.
41 citations
TL;DR: In this paper, the authors examined the effect of external radiation, oxygen concentration, and inclination angle of combustible material on the development of fire and found that fire development is influenced by many factors, such as oxygen concentration and external radiation.
Abstract: Fire development is influenced by many factors, such as oxygen concentration, external radiation, and the inclination angle of the combustible material. This article examines the effect of these fa...
13 citations
Cites background or result from "Flame heat fluxes and correlations ..."
...For downward flame spread, Fernandez-Pello (1977a), Hirano and Sato (1975), Magee and Mcalevy (1971), and Williams (1977) found that the flame spread rate is dominated by the temperature of the solid in front of the pyrolysis front....
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...For upward flame spread under external radiation, similar results were found (Delichatsios, 2000; Delichatsios et al., 1994; Fernandez-Pello, 1977b; Saito et al., 1989)....
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TL;DR: In this paper, an evaluation of four tests that could be used for controlling floor coverings, namely the Cone Calorimeter, the Flooring Radiant Panel (FRP), the LIFT Apparatus and the Early Fire Hazard Test (EFH), was conducted.
Abstract: The potential of building materials to contribute to fire growth and spread has led to extensive regulatory control. Various and numerous small-scale tests are used to simulate and characterize flammability, flame spread and smoke production. Recently, the Fire Science and Technology Laboratory at CSIRO conducted an extensive research project into the performance in fire of flooring and floor coverings. Specifically, this paper focuses on an evaluation of four tests that could be used for controlling floor coverings, namely the Cone Calorimeter, the Flooring Radiant Panel (FRP), the LIFT Apparatus and the Early Fire Hazard Test (EFH). The reason behind the test selection was that the first three tests are internationally recognized while the fourth is a valuable, well-documented and validated Australian test that is referred to in the Building Code of Australia. EFH was originally developed to regulate wall lining materials but its use has been extended to regulate almost everything else, including floor coverings. Detailed test measurements in these apparatuses included ignition times in the Cone and EFH, critical heat flux in the Cone, FRP, LIFT and EFH, and rate of heat release and smoke yield in the Cone and EFH. Comparisons of similar parameters were made to investigate consistency of test results within the present regulatory requirements for floor coverings. In addition, prediction of flooring material behavior in each of these tests based on results from the rest of the tests was explored. Based on this comparison, the significance of each test with regard to providing information for flammability properties of relevance to control of floor coverings is established.
7 citations
Cites background from "Flame heat fluxes and correlations ..."
...This parameter determines a characteristic flame spread speed (Delichatsios, 2000)....
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TL;DR: In this article, an analytical expression of the universal mass transfer B-number was derived, which applies to semi-transparent flames with external radiation, and new parameters were defined and illustrated, such as the mass transfer equivalent absorption coefficient, specific radiant heat feedback and radiation factor.
6 citations
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TL;DR: In this article, heat transfer and flame height results are presented for wall samples burned at varying levels of external irradiance, and an approximate theoretical analysis is included to serve as a guide to identifying the important variables and their relationship for correlation purposes.
Abstract: New concepts are addressed for predicting the flame spread on materials from laboratory measurements. It focuses on heat transfer which precipitates and precedes upward flame spread on a vertical surface. Six materials have been featured in this study as well as in past related studies. Their flame spread properties are presented. In this particular study heat transfer and flame height results are presented for wall samples burned at varying levels of external irradiance. Also complementary results are presented for methane line burner wall fires. An approximate theoretical analysis is included to serve as a guide to identifying the important variables and their relationship for correlation purposes. Experimental results yield flame height proportional to energy release rate to the 2/3 power, and wall heat flux distributions are roughly correlated in terms of distance divided by flame height. These correlations appear to at least hold for the scale of these experiments: flame heights of 0.3 to 1....
135 citations
TL;DR: In this paper, a comprehensive study on the flammability, flame spread, and flame extinction behaviors of polymethylmethacrylate slabs and cylinders is presented, and the results show that flame spread behavior is accelerating for upward spread and nonaccelerating for downward spread.
105 citations
52 citations
Book•
01 Jan 1986
39 citations
TL;DR: In this paper, it was shown that turbulent upward flame spread on noncharring materials (for pyrolysis lengths less than 1.8 m) can be directly predicted by using measurable flammability parameters.
25 citations