添加微量液體對不同密度顆粒於旋轉鼓內分離機制的影響

溫士鋒(Shi-Feng Wen)

指導教授 ： 蕭述三

國立中央大學/工學院/機械工程研究所碩士在職專班/碩士(2015年)

摘要

本論文是以類二維的精密旋轉鼓為實驗設備，並以實驗的方式探討添加微量液體含量及旋轉鼓轉速快慢，對不同密度顆粒在旋轉鼓中分離機制的影響。運用高解析及高速攝影機搭配影像分析及粒子追蹤的方法，分析及量測分離強度、安息角(Angle of Repose)、速度場變化等影響分離機制的重要指標。實驗結果顯示添加微量液體含量的多寡與轉速的快慢，會使混合的現象呈現較佳，也代表此兩項參數對於密度分離機制有顯著的影響；隨著無因次液體含量增加，顆粒體間的液橋隨之增厚，平均架橋數也跟著增多，顆粒間彼此吸附力量增加，因此會形成較大的安息角，並抑制分離效應；而當轉速增加時，重顆粒平均流動速度變快，轉速的提升代表外界供給系統的能量變大，因此重顆粒能有較大的動能與較快的速度，也使得間隙液體對速度的影響慢慢變小。實驗結果亦發現最終分離強度會隨著安息角變大而產生線性遞減的關係且無關於轉速及微量液體含量；本研究也試著將過去尺寸效應的數據結果與本研究密度效應的結果相互比較，結果顯示安息角與最終分離強度仍是維持線性遞減的關係。

關鍵字

旋轉鼓 ； 液體含量 ； 分離強度 ； 安息角 ； 流場速度

並列摘要

The density-induced granular segregation phenomenon of wet granular materials was experimentally studied in a quasi-2D rotating drum. The motions of the granular materials were recorded by a high-speed camera. Image processing technology and particle tracking method were employed to measure the segregation intensity, repose angle and the velocities of heavy particles. The effects of liquid content and rotation speed on segregation index, angle of repose, and velocity field in the rotating drum were investigated and discussed in this paper. The experimental results indicate that the liquid content and rotation speed have significant influences on density-induced granular segregation. The segregation intensity is mitigated with the increase of liquid content because of the stronger cohesive force between particles. It also shows that segregation intensity is reduced with the increasing of rotation speed. The segregation index is demonstrated to be decreased with the increase of the repose angle of wet granular materials, regardless of the addition of liquid content, liquid viscosity, rotation speed, density effect and size effect.

並列關鍵字

liquid content ； segregation ； angle of repose

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