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Mechanism of flame propagation through combustible particle clouds
An experimental study has been conducted on the mechanisms of flame propagation through combustible particle clouds of pure 1-octadecanol. The particle clouds provided for the experiments consisted of particles of a few tens of micron in mean diameter. Behaviour of flame propagating through the particle clouds and related phenomena have been examined by using direct light emission, schlieren and laser scattering images simultaneously recorded by a CCD video camera. After ignition, a flame kernel grows within a yellow luminous zone whose outline is of an irregular shape. A smooth-shaped schlieren front, which indicates a thermal boundary, propagates at 4 mm to 8 mm ahead of the outline of the luminous zone. Inside the schlieren front, dispersed blue flames appear but no smaller particles can be seen. This results indicates that across the schlieren front, smaller particles (most of them are about 10 micron to 20 micron in diameter) rapidely gasify, while the gasification of particles with a diameter larger than 80 micron is delayed, and vapour lumps are formed behind the schlieren front. These lumps then burn to form circular dispersed blue flames. It has also been revealed that the average schlieren front velocity increases with the number density of small particles, while it depends only slightly on the mean diameter of combustible particles. This fact implies that the flame propagation is mainly supported by the combustion of small particles gasifying across the schlieren front.
Mechanism of flame propagation through combustible particle clouds
An experimental study has been conducted on the mechanisms of flame propagation through combustible particle clouds of pure 1-octadecanol. The particle clouds provided for the experiments consisted of particles of a few tens of micron in mean diameter. Behaviour of flame propagating through the particle clouds and related phenomena have been examined by using direct light emission, schlieren and laser scattering images simultaneously recorded by a CCD video camera. After ignition, a flame kernel grows within a yellow luminous zone whose outline is of an irregular shape. A smooth-shaped schlieren front, which indicates a thermal boundary, propagates at 4 mm to 8 mm ahead of the outline of the luminous zone. Inside the schlieren front, dispersed blue flames appear but no smaller particles can be seen. This results indicates that across the schlieren front, smaller particles (most of them are about 10 micron to 20 micron in diameter) rapidely gasify, while the gasification of particles with a diameter larger than 80 micron is delayed, and vapour lumps are formed behind the schlieren front. These lumps then burn to form circular dispersed blue flames. It has also been revealed that the average schlieren front velocity increases with the number density of small particles, while it depends only slightly on the mean diameter of combustible particles. This fact implies that the flame propagation is mainly supported by the combustion of small particles gasifying across the schlieren front.
Mechanism of flame propagation through combustible particle clouds
Mechanismen der Flammenausbreitung in brennbaren Teilchenwolken
Chen, J.L. (author) / Dobashi, R. (author) / Hirano, T. (author)
Journal of Loss Prevention in the Process Industries ; 9 ; 225-229
1996
5 Seiten, 9 Bilder, 1 Tabelle, 5 Quellen
Article (Journal)
English
Flame Propagation Through Combustible Particle Clouds
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