2002 Fiscal Year Final Research Report Summary
Flushing Phenomenon of Fine power
| Project/Area Number |
13650185
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Kyushu Institute of Technology |
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Principal Investigator |
TOMIYAMA Yuji Kyushu Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (60039104)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Flushing / Fine Power / Adhesion Property / Powder Head / Air Pressure / Flooding / Voidage / Handling |
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| Research Abstract |
Generally, fine power cannot flow out through a small orifice or narrow channel due the cohesiveness. However, if the power contains air, unexpected fluidization occurs and the power flows out of the orifice or channel like a liquid. We call this a flushing phenomenon, which becomes a possible source of troubles in handling of power in industry. We have explained a mechanism of flushing phenomenon as follows; when the air pressure in the void of power is increased by some external stimulus, the pressure difference is produced between the power and the outside, which, in turn, produces air flow from power to the outside through a small orifice or narrow channel and the power is spouting entrained by the air flow. Kuchii et al. increases the air pressure of power in a cylinder by applying a piston load on the free surface and Okamura et al. produces a periodical air pressure by applying vertical vibration on the power bed. However, the flushing phenomenon in practice is produced by the different means.
In this work, we generated air pressure in power in a cylindrical vessel by the impact of falling aerated power on the surface, and at the same time a high voidage power bed was created. Then the flushing phenomenon was produced through the bottom orifice. Furthermore, we found that the power bed of higher voidage can keep the flushing by the weight of the powder bed. We generated the flushing by fluidizing the power bed introducing air from the vessel bottom for a given voidage and then opening the bottom orifice as well as stopping the aeration. By this method we can consider the flushing avoiding the complicated phenomenon involved by the power impact. We found out the effects of air pressure, voidage, bed height and orifice diameter on the flushing phenomenon.
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