Study of Fluidization of Cohesive Powder by Mechanical Vibration

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Experimental and numerical studies of spouting of powder from vertically vibrated bed are performed. The powder, especially fine and cohesive one, spouts out vigorously through a side orifice of the vertically vibrated vessel in which the powder is contained, provided that the vibration intensity is greater than unity. We examine the mechanism of this phenomenon and the relationship between the efflux rate and the vibration condition. The interstitial air pressure in the bed that periodically fluctuates is measured and is compared to the results of the numerical analysis considering the relative motion of the powder bed to the vibrated vessel and percolation air flow. The outflow behavior of powder is observed by using a high-speed video camera. The experimental and the numerical results indicate that the powder spouts out with periodic air outflow, which is generated in response to the change of the gap between the bed and the vessel base. Furthermore, it is found that the efflux rate of powder is in proportion to the generated air pressure and in inverse proportion to the vibration frequency.