粉體振盪程序之三維離散元素分析

Three-Dimensional Discrete Element Method Analysis on the Vibrating Processes of a Particulate System

張景翔(Ching-Hsiang Chang)

指導教授 ： 童國倫

中原大學/工學院/化學工程研究所/碩士(2003年)

https://doi.org/10.6840/cycu200300281

摘要

本研究以離散元素法(Discrete Element Method, DEM) 探討粉體振盪程序中，粉體的運動型態與粒子的偏析、篩析等現象。首先開發完成粉體振盪模擬系統， 並以篩析操作為驗證與初步應用對象。採篩析操作為對象之特點有(1)實驗系統簡單(2)力作用模式涵蓋最廣， 且(3)粒子運動模式最為複雜， 如粒子與粒子間的碰撞，粒子與週期性簡諧運動壁面的碰撞及粒子的篩落機制等。因此，本
研究進而分別探討二維及三維粉體振盪系統中，不同振盪頻率、振幅下粉體的整體運動行為及粒子的偏析現象，並延伸分析不同振盪操作條件下粉體之篩分操作的微觀現象，以及篩網結構對模擬結果之影響。

模擬結果顯示，在垂直振動床中，粉體床隨著振動加速度增加會分別產生堆積、黏合、膨脹、波浪、及拱橋等五種現象，與文獻中之實驗觀察結果相當吻合。此外，本研究在不同形狀容器的比較上發現，在圓柱形容器中的運動型態比較接近二維粒子床，床內具有相當顯著的粒子對流型態；而方形容器中的粒子交互作用較不明顯。在振盪篩析的應用研究上發現篩網結構對模擬結果之影響相當大，以編織篩網取代文獻中之簡化形篩網，可提高實驗結果之吻合度。此外，若振動床內的粉體呈拱橋式運動，則具有掃除堵塞於篩網上之粒子的效果， 也提高了篩析的效率。

關鍵字

振動 ； 粒子 ； 篩網 ； 篩析 ； 粉體 ； 模擬 ； 散元素法

並列摘要

In this study, vibrating and sieving processes of a particulate system have been analyzed
microscopically by Discrete Element Method (DEM). A 3-D simulation procedure for particulate vibrating system analysis was developed and was applied on the exploration of a sieving process. The sieving process includes highly complicated interactions among particles, simple harmonic motion wall and screen due to both of vibrating and sieving process. These are also the merits for thoroughly checking the validation of the developed simulation procedure. The developed simulation procedure was then applied to examine the bulk motion mechanisms of particulate movement and segregation in both of 2-D and 3-D
vibrating beds. In the application on a sieving process, emphasis was placed on the effect of
screen structure and operating conditions such as amplitude and frequency.
The simulation results show that there are heap, coherent, expansion, wave, and arching motion mechanisms during the increase of the vibrational acceleration. The obtained regimes of particulate motion agrees well with that observed in the previous literature qualitatively. In addition, to compare with the motion of powder in different
shape containers, the motion in cylinder one is more similar to two-dimensional system with convection, but the relative velocity in a
square one is unclear. In the research of sieving process, because the structure of screen is the important factor of sieving process, the simulation result of sieving rate is more similar to the experiment result by woven screen instead of simplified screen. In addition, the simulation
results of sieving also reveal that the powder in vibration possesses the function to remove the particles blinding the holes of the screen, and raise the sieving capability.

並列關鍵字

particle ； vibration ； DEM ； powder ； screen ； simulation ； sieving

參考文獻

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Rheology, 35 721-734 (1991).

Aoki, K. M. and T. Akiyama, “Control parameter in granular convection,” The American

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