自由落下粉体ジェットの落下速度に及ぼす粒子物性の影響(流体工学,流体機械)

概要

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We measured the velocity and number density of powder jet falling from a hopper by using a phase Doppler anemometer and obtained the following results. The center line velocity of powder jet near the hopper exit is close to the free falling velocity of a single particle in disregared of the fluid drag, which is independent of the diameter, density and mass flow rate of particle, and far from the exit tends to approach the terminal settling velocity of a single particle. When the particle diameter is small and the mass flow rate is increased, the ratio of the center line velocity to the terminal velocity increases. The axial fluctuation velocity profile of powder jet takes a minimum at the jet axis and after taking a maximum decrases toward the outer edge. The profile becomes flat when the mass flow rate is small and the falling distance is increased. The number density profile takes a maximum near the jet axis and rapidly decreases toward the outer edge. The center line number density of the small particle is larger than that of the large particle. It is inferred that the dimensionless mass flow rate of the entrained air is increased with increasing the falling distance, being independent of particle size and density.
社団法人日本機械学会の論文
2004-08-25