振動床於弱振動下顆粒分離機制研究; Segregation Mechanisms in the vibrated granular bed under weakly vibration

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题名:	振動床於弱振動下顆粒分離機制研究;Segregation Mechanisms in the vibrated granular bed under weakly vibration
作者:	方啟守;Chi-Shou Fang
贡献者:	機械工程研究所
关键词:	振動床;梯度材料;弱振動;weakly vibration;vibrated granular
日期:	2004-07-12
上传时间:	2009-09-21 11:46:42 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	混合顆粒體在振動床中，會有大顆粒向上昇，而小顆粒向下沈的分離現象，本文即是探討在圓柱振動床中影響粒子分離機制的原因。由於振動床的分離現象在實驗中極易受到各種因素變化的影響，因此本文討論的方向有三部分：第一部分為類固體層高度實驗，藉由這個部分的實驗可以得知在不同振動條件下所對應的類固體層高度，同時知道各個頻率能達到充分流動現象之最小振動加速度。第二部分則是幾何分離實驗，由第一部分的實驗結果來進行尺寸分離的實驗，並找出能使顆粒體分離的振動條件。第三部份則為對流效應實驗，這個部分的實驗，整體的振動強度較之前兩個部分的實驗強烈，顆粒體受到較大的振動加速度在實驗容器內作對流的運動。由前述的三個實驗結果，可以定義出三種不同的運動機制。在不同運動機制下的顆粒體，有著不同的運動行為，微弱運動機制下的顆粒活動並不是相當活躍，因此實驗容器內會有類固層的存在；幾何分離機制下的顆粒，因為有適當的給予能量，所以不同尺寸的粒子會有分離的情形發生；對流運動機制下的顆粒，因為受到強烈的振動加速度，粒子在容器內做劇烈的對流運動，主要的原因是受迴流胞的影響。 In vibration granular bed, the larger particles existed in the upper regions of the bed, and the small ones stayed in the lower regions of the bed. The study investigated the effects on segregation mechanisms in a cylindrical vibrated bed. The three main experiments were performed to study the segregation mechanisms in a vibrated granular bed. First, the solid-like experiment was performed to investigate the minimum vibration acceleration under the different vibration frequencies, which all the particles in the bed flowed allover the bed. Second, the geometrical experiment was performed to investigate the vibration conditions causing the particle segregation. Last, the effects of convection strength on particle segregation were be examined by performing convection roll experiment. The three different motion mechanisms were found in this study. The solid-like layer existed in weak motion mechanism where the vibration conditions were weak. In geometrical mechanism regions, the binary mixture of particles segregated due to different diameter of particles. For the stronger vibration conditions, the effects of convection strength on particles’ motions in the vibrated granular bed were dominant.
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