剪力槽內大小顆粒體的分離研究; The segregation of different size particles in a shear cell

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Title:	剪力槽內大小顆粒體的分離研究;The segregation of different size particles in a shear cell
Authors:	簡思佳;Szu-Chia Chien
Contributors:	機械工程研究所
Keywords:	顆粒;分離強度;剪力槽;分離率;segregation rate.;segregation strength;particle;shear cell
Date:	2007-06-13
Issue Date:	2009-09-21 11:58:58 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	近來顆粒體的混合與分離在一般日常生活與工業技術上皆有廣泛且重要的發展，剪力槽內粒子流的相關研究大多著重於混合與傳輸機制，顆粒體分離現象方面，只要顆粒體尺寸、密度上有些微的差異就足以產生不同的顆粒體分離現象。本文主要以剪力槽中粒子流動的實驗來探討轉盤的切線速度、粒徑比及顆粒初始配置對大小顆粒體分離的影響。本文所使用的剪力槽是上盤固定、下盤轉動的環形槽，實驗中有0.66m/s、0.88m/s、1.10m/s、1.32m/s及1.54 m/s等五種不同的轉盤的切線速度，大小顆粒的粒徑比有1.15、1.33、1.5及2.0等四種。當底盤轉動後，剪力槽內會形成大顆粒往上、小顆粒往下的分離現象。本文的實驗即以追蹤大顆粒的位置來分析大顆粒的平均高度及濃度分佈，並且定義出分離強度Is，以作為衡量分離現象的指標。由實驗的結果分析顯示，各種實驗條件下，分離強度隨著時間的增加而增強，並且呈指數關係成長，因此可利用曲線擬合算出初始階段分離的速率，即分離率k。當轉盤的切線速度越快或粒徑比越大時，分離率越快且可達到較高的分離強度；所以在本研究粒徑比範圍內推斷出影響分離現象為粒徑比較顯著於底盤速度。 In this study, an annular shear cell is used to investigate the influences of bottom velocity, diameter ratio and initial pattern arrangement on the segregation of particles with different sizes. The annular shear cell is consisted of a stationary top-disk and a rotating bottom-disk. Five bottom-disk velocities (0.66 m/s, 0.88 m/s, 1.10 m/s, 1.32 m/s and 1.54 m/s) and four diameter ratio (1.15, 1.33, 1.5 and 2.0) are used in our experiments. With the rotating bottom-disk, the big particles move to the upper section, while the small particles fall down to the lower section. This study traces the positions of big particles to analyze their averaged heights and concentration profiles. The segregation strength, Is, is defined as an index to quantify the degree of segregation. In all cases, the segregation strength increases exponentially with increasing rotating time. The segregation rate, k, at initial stage can be calculated from a least square curve fitting. With larger bottom-disk velocity or larger diameter ratio, the segregation rate is faster, and the segregation strength of steady status is also larger.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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