Opposed Flame Spread over Polyethylene Under Variable Flow Velocity and Oxygen Concentration in Microgravity

Kobayashi, Yoshinari; Terashima, Kaoru; Borhan, Muhammad Arif Fahmi bin; Takahashi, Shuhei

doi:10.1007/s10694-019-00862-4

Cited by 12 publications

(5 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…in the legend) as a function of X O2 for the Type#1, Type#2 and Type#3 wires. As expected from experimental observations in microgravity for electrical wires [20,33], the FSR increases with X O2 for all the cases owing to an increase in flame temperature, which results in an increase of the flame heat flux transferred to the solid surface. This behavior is well captured by the model.…”

Section: Flame Spread Ratesupporting

confidence: 79%

An engineering model for creeping flame spread over idealized electrical wires in microgravity

Coimbra¹,

Li²,

Guibaud³

et al. 2023

Comptes Rendus. Mécanique

View full text Add to dashboard Cite

Flame spread over an insulated electrical wire is a major source of fire scenario in a space vehicle. In this work, an engineering model that predicts the creeping flame spread over cylindrical wires in microgravity is developed. The model is applied to interpret experimental data obtained in parabolic flights for wires composed by a 0.25 mm radius nickel-chromium (NiCr) metallic core coated by low-density polyethylene (LDPE) of different thicknesses ranging from 0.15 mm to 0.4 mm. The model relies on the assumption that, in the pyrolysis region, the NiCr and the LDPE are in thermal equilibrium. This assumption is supported by more detailed numerical simulations and the model reduces then to solving the heat transfer equations for both NiCr and LDPE in the pyrolysis region and in the region ahead of the flame front along with a simple degradation model for LDPE, an Oseen approximation of opposed oxidizer flow and an infinitely fast gas-phase chemistry. The flame spread rate (FSR) is controlled by two model parameters, which are measurable from intrinsic material and ambient gas properties: the convective flame heat flux transferred to the solid ahead from the flame front and the gaseous thermal heat length near the flame front. These parameters are then calibrated from experimental data for a given wire geometry and the calibrated model is validated against experimental data for other wire geometries and ambient conditions. The heat transfer mechanisms ahead of the pyrolysis front are investigated with a special emphasis on the LDPE thickness and the conductivity of the metallic core. In addition to NiCr, metallic cores of lower and higher conductivities are considered. The polymer is shown to be thermally thick for all tested wire geometries and core conductivities. The flame heat flux is found to dominate the heat transfer in the preheat zone where it applies. The core has

show abstract

Section: Flame Spread Ratesupporting

confidence: 79%

An engineering model for creeping flame spread over idealized electrical wires in microgravity

Coimbra¹,

Li²,

Guibaud³

et al. 2023

Comptes Rendus. Mécanique

View full text Add to dashboard Cite

show abstract

“…However, it still is a big approximation to use groundbased experiments to guess the material flammability and fire behaviors in microgravity. Especially for thermoplastic materials, the flow and dripping of melts driven by gravity may change the flammability, flame-spread rate (Kobayashi et al 2020), andextinction limit (Miyamoto et al 2016). Thus, the conventional ground-based experiments may no longer reflect worse fire scenarios, which can be referred to for the fire safety in microgravity.…”

Section: Introductionmentioning

confidence: 99%

Flame Spread over Polyethylene Film: Effects of Gravity and Fuel Inclination

Zhu

Huang

Wang

2022

Microgravity Sci. Technol.

View full text Add to dashboard Cite

The flammable thermoplastics are widely used in our daily life and manned space travels in microgravity, posing a potential fire risk. This work studies the flame spread along with the thin polyethylene (PE) film (15-100 µm) in the microgravity drop tower and normal gravity. Microgravity flame spread faster than vertically downward flame spread in normal gravity due to the weak buoyancy flow and greater flame preheating length. For the ultra-thin film, the influence of melting on the opposed flame spread is negligible. The upward flame spread rate reaches a maximum constant (45 ± 10 mm/s for 20 μm film) when the inclination angle is larger than 30°, due to the dripping removal of molten fuel. The upward flame spread rate changes under the competition between the enhanced flame heating by buoyancy and the dripping removal of the molten fuel. The vertically upward spreading flame cannot be maintained due to the dripping removal of the molten fuel, and a critical extinction condition was determined and analyzed. This work provides valuable data on flame dynamics in plastic films and can help develop more sophisticated material flammability tests for fire safety in space travel.

show abstract

“…Unique space fire experiments have been conducted in the International Space Station [5,6], unmanned spacecraft [7], and a satellite [8] to understand the long-term micro-gravity combustion and fire phenomena. The fire dynamics small and thin fuels are also explored through ground-based microgravity experiments using drop towers [9] and parabolic flights [10][11][12][13][14]. In addition, combustion and fire experiments under reduced pressures [15][16][17] and a narrow channel [18] are applied to lower the influence of buoyancy and simulate low-gravity environments on Earth.…”

mentioning

confidence: 99%

“…Thus, microgravity also provides an ideal environment for fundamental combustion research [4]. Unique phenomena for flame spread in microgravity over thin paper [9], thick plastic plates [7,10,18], cylindrical rods [8,17], spherical fuels [5] and electrical wires of different thicknesses [11,12,14,20] are observed, and the influence of airflow speed, direction, and oxygen concentration on flame stability are investigated.…”

mentioning

confidence: 99%