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Journal ArticleDOI

Microgravity flammability boundary for PMMA rods in axial stagnation flow: Experimental results and energy balance analyses

01 Jun 2017-Combustion and Flame (Elsevier)-Vol. 180, Iss: 180, pp 217-229
TL;DR: In this article, a series of concurrent-flow rod flammability tests were conducted in microgravity aboard the International Space Station (ISS), where a small flow duct was used to create 0 to 55 cm/s flows past three sizes of clear and black PMMA rods.
About: This article is published in Combustion and Flame.The article was published on 2017-06-01. It has received 46 citations till now. The article focuses on the topics: Premixed flame & Adiabatic flame temperature.
Citations
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Journal ArticleDOI
TL;DR: In this paper, a large-scale flame spread experiment was conducted inside an orbiting spacecraft to study the effects of microgravity and scale and to address the uncertainty regarding how flames spread when there is no gravity and if the sample size and the experimental duration are, respectively, large enough and long enough to allow for unrestricted growth.

59 citations

Journal ArticleDOI
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

Journal ArticleDOI
TL;DR: In this paper, the effect of the type of insulation, the ratio of insulation to core thickness, or the thermal properties of the core, on the wire fire behaviors was investigated.

48 citations

Journal ArticleDOI
TL;DR: In this article, the authors revisited the problem of opposed fire spread under limited and excessive oxygen supply and reviewed various near-limit fire phenomena, as recently observed in flaming, smoldering, and glowing spread under various environment and fuel configurations.

40 citations

Journal ArticleDOI
01 Jan 2019
TL;DR: In this article, the authors identify the transition from opposed flame spread to fuel regression under varying conditions, including sample size, opposed flow velocity, pressure, oxygen concentration, external radiation, and gravity level.
Abstract: The spread of flames over the surface of solid combustible material in an opposed flow is different from the mass burning (or fuel regression) in a pool fire. However, the progress of a flame front over a solid fuel includes both flame spread and fuel regression, but the difference between these two processes has not been well clarified. In this work, experiments using cylindrical PMMA samples were conducted in normal gravity and in microgravity. We aim to identify the transition from opposed flame spread to fuel regression under varying conditions, including sample size, opposed flow velocity, pressure, oxygen concentration, external radiation, and gravity level. For a thick rod in normal gravity, as the opposed flow increases to 50–100 cm/s, the flame can no longer spread over the fuel surface but stay in the recirculation zone downstream of the cylinder end surface, like a pool fire flame. The flame spread first transitions to fuel regression at a critical leading-edge regression angle of α ≈ 45°, and then, flame blow-off occurs. Under large opposed flow velocity, a stable flat blue flame is formed floating above the rod end surface, because of vortex shedding. In microgravity at a low opposed flow (

30 citations

References
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Journal ArticleDOI
TL;DR: In this paper, the structure of steady state diffusion flames is investigated by analyzing the mixing and chemical reaction of two opposed jets of fuel and oxidizer as a particular example, and an Arrhenius one-step irreversible reaction in the realistic limit of large activation energies.

792 citations

Journal ArticleDOI
TL;DR: Laminar counterflow diffusion flames are generally referred to as the pure diffusion flame as discussed by the authors, and they can be classified into four types: (i) counterflow between two opposed jets, (ii) flat, counter-flow diffusion flame between two matrix burners, (iii) counter flow diffusion flame in the forward stagnation region of a spherical or hemispherical porous burner, and (iv) the counterflow diffuser flame in a cylindrical porous burner.

374 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis of diffusion flame extinction in the stagnation point region of a condensed fuel has been made including radiative heat loss from the fuel surface, and the extinction boundary consists of a blowoff and a radiative extinction branch.

187 citations

Journal ArticleDOI
TL;DR: A review of the literature pertaining to flame impingement heat transfer is presented in this article, where studies related to different modes of heat transfer, flame shapes and flame stabilization are considered Investigations of previous work for different experimental configurations, operating conditions, burner geometry, separation distance and stagnation target with instrumentation are compared.

128 citations

Journal ArticleDOI
01 Jan 1989
TL;DR: In this article, the flame behavior is observed to depend strongly on the magnitude of the relative velocity between the flame and the atmosphere, and a low velocity quenching limit is found in low oxgen environments.
Abstract: Diffusion flame spread over a thin solid fuel in quiescent and slowly moving atmospheres is studied in microgravity. The flame behavior is observed to depend strongly on the magnitude of the relative velocity between the flame and the atmosphere. In particular, a low velocity quenching limit is found to exist in low oxgen environments. Using both the microgravity results and previously published data at high opposed-flow velocities, the flame spread behavior is examined over a wide velocity range. A flammability map using molar oxygen percentages and characteristic relative velocities as coordinates is constructed. Trends of flame spread rate are determined and mechanisms for flame extinction are discussed.

122 citations