Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Velocity and number density profiles of particles across upward and downward flame propagating through iron particle clouds
Behaviors of particles across upward and downward flame propagating through iron particle clouds have been recorded on photomicrographs by using a high-speed video camera with a microscopic optical system. The velocity profiles of iron particles across flames were measured by using the high-speed photomicrographs, and the number density profiles of iron particles near the flames were calculated by using the velocity profiles. It is shown that the number density of iron particles changes in the range of x smaller than 11.0 mm, where x is the distance from the leading edge of the combustion zone. The number density increases with the decrease of x in the range 0 < x < 11.0 mm, reaches a maximum at the leading edge of the combustion zone, and then decreases. For upward propagating flame, the maximum value of the number density is about 3.5 times larger than that at the region far ahead of the flame (x > 10.0 mm), however, for downward propagating flame, it is only 2.3 times larger than that at the region far ahead of the flame. This phenomenon should also exist in other types of particle cloud flames and liquid spray flames where particles or droplets move at velocities different from gas velocity. The accelerated gas flow ahead of the flame results in the change of the relative velocity of particles, resulting in the increase of number density. Such increase is supposed to occur in any two-phase combustion systems in which the slip between the particle and gas velocities is significant. The increase of number density just ahead of the flame is supposed to influence the lower flammability limits of a combustible particle cloud.
Velocity and number density profiles of particles across upward and downward flame propagating through iron particle clouds
Behaviors of particles across upward and downward flame propagating through iron particle clouds have been recorded on photomicrographs by using a high-speed video camera with a microscopic optical system. The velocity profiles of iron particles across flames were measured by using the high-speed photomicrographs, and the number density profiles of iron particles near the flames were calculated by using the velocity profiles. It is shown that the number density of iron particles changes in the range of x smaller than 11.0 mm, where x is the distance from the leading edge of the combustion zone. The number density increases with the decrease of x in the range 0 < x < 11.0 mm, reaches a maximum at the leading edge of the combustion zone, and then decreases. For upward propagating flame, the maximum value of the number density is about 3.5 times larger than that at the region far ahead of the flame (x > 10.0 mm), however, for downward propagating flame, it is only 2.3 times larger than that at the region far ahead of the flame. This phenomenon should also exist in other types of particle cloud flames and liquid spray flames where particles or droplets move at velocities different from gas velocity. The accelerated gas flow ahead of the flame results in the change of the relative velocity of particles, resulting in the increase of number density. Such increase is supposed to occur in any two-phase combustion systems in which the slip between the particle and gas velocities is significant. The increase of number density just ahead of the flame is supposed to influence the lower flammability limits of a combustible particle cloud.
Velocity and number density profiles of particles across upward and downward flame propagating through iron particle clouds
Geschwindigkeitsprofil und Partikeldichte in Eisenstaubwolken bei aufwärts oder abwärts gerichteter Flammausbreitung
Sun, Jinhua (Autor:in) / Ritsu, Dobashi (Autor:in) / Toshisuke, Hirano (Autor:in)
2006
7 Seiten, 8 Bilder, 1 Tabelle, 18 Quellen
Aufsatz (Konferenz)
Englisch
Aufwärtsbewegung , Dichte (Anzahl pro Volumen) , Eisen , Entflammbarkeitstemperatur , Flammausbreitung , Gasströmung , Geschwindigkeitsprofil , Konferenzbericht , Literaturübersicht , Metallpulver , Mikrophotographie , Partikelgröße , Partikelströmung , Staubexplosion , Strömungsgeschwindigkeit , Teilchendichte , Versuchsaufbau
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