顆粒形狀對三維旋轉滾筒中軸向偏析影響之探討

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题名:	顆粒形狀對三維旋轉滾筒中軸向偏析影響之探討
作者:	王懌承;WANG, YI-CHENG
贡献者:	機械工程學系
关键词:	旋轉鼓;顆粒形狀;顆粒分離;動態安息角;Rotating drum;Particle shape;Particle segregation;Dynamic angle of repose
日期:	2025-08-18
上传时间:	2025-10-17 13:14:46 (UTC+8)
出版者:	國立中央大學
摘要:	顆粒材料由多種物理性質組成，廣泛應用於日常生活與各類產業流程中。其中旋轉鼓常被用於顆粒的混合、乾燥與造粒等操作，並發展出多種工業設備。然而，顆粒間交互作用與外部條件之影響，使其顆粒系統內部難以預測。本研究使用三維旋轉滾筒，透過改變轉速及顆粒縱橫比。以瞭解不同縱橫比之圓柱體顆粒與球形顆粒二元混合後所產生的軸向偏析行為。本研究利用直徑dP = 5 mm的ABS球形顆粒與縱橫比AR = 0.5、AR = 1、AR = 2、AR = 3的相同表面材質相同體積之ABS塑膠圓柱顆粒。並透過高速攝影機及數位攝影機進行影像拍攝，再搭配粒子影像測速技術PIV (particle image velocimetry)和MATLAB進行後續的影像處理。分析顆粒濃度分布、動態安息角估算、速度場分析等，來了解顆粒形狀對軸向偏析產生的影響。實驗結果顯示，在高轉速的條件下，低縱橫比之圓柱體顆粒於旋轉滾筒端壁會迅速聚集，球形顆粒則集中於中心位置，呈現明顯的軸向偏析；相較之下，高縱橫比之圓柱體顆則會因為顆粒間的互鎖效應抑制其移動性，使偏析程度顯著降低。軸向偏析指數之結果亦驗證上述趨勢，顯示低縱橫比之圓柱體顆粒於各轉速條件下，皆具最高偏析程度，且隨著轉速增加，偏析現象達到飽和所需時間縮短，但對最終偏析強度之提升影響有限。此外，徑向濃度分析結果指出，顆粒系統在軸向偏析初期會先產生明顯的徑向偏析，最終形成兩端濃度高、中心濃度低的穩定分布，表示軸向偏析不僅發生於顆粒系統表層，亦影響了顆粒內部結構。速度場與邊壁高度分析發現到，端壁區域具有較高的顆粒速度與高度，驅動表層顆粒自端壁向中心行程回流，進而形成穩定的軸向流動結構。此機制在低縱橫的顆粒系統中效果最為顯著，反映出顆粒形狀對偏析行為具有主導作用。 ;Granular materials are widely used in daily life and industry. Rotary drums are commonly used for mixing, drying, and granulation. However, complex particle interactions and external factors make their internal behavior hard to predict. This study utilizes a three-dimensional rotating drum to investigate axial segregation behavior resulting from binary mixing of cylindrical particles with varying aspect ratios and spherical particles, under different rotational speeds. ABS spherical particles with a diameter of dP = 5mm, and ABS cylindrical particles of identical surface material and volume, but with aspect ratios of AR = 0.5、1、2、3, were used. High-speed cameras and digital video recording were employed for image capture, followed by image processing using Particle Image Velocimetry (PIV) and MATLAB. The analysis focused on particle concentration distribution, dynamic repose angle estimation, and velocity field characterization to evaluate the effect of particle shape on axial segregation. Results show that under high rotational speed, cylindrical particles with lower aspect ratios quickly accumulate near the end walls of the drum, while spherical particles concentrate near the center, resulting in significant axial segregation. In contrast, higher aspect ratio cylindrical particles exhibit reduced mobility due to interlocking effects between particles, leading to noticeably suppressed segregation. The axial segregation index corroborates these trends, indicating that low aspect ratio cylindrical particles consistently exhibit the highest degree of segregation under all tested speeds. Moreover, while higher rotation speeds shorten the time required to reach saturation in segregation, they have limited impact on increasing the final intensity of segregation. Radial concentration analysis reveals that prominent radial segregation precedes axial segregation in the early stages, ultimately forming a stable distribution characterized by higher particle concentration at both ends and lower concentration in the center. This indicates that axial segregation occurs not only on the surface but also affects the internal structure of the granular bed. Analysis of velocity fields and Side wall height further demonstrates that the end wall regions exhibit higher particle velocities and height, driving surface particles to flow back from the end walls toward the center, thus forming a stable axial flow structure. This mechanism is most pronounced in systems with low aspect ratio particles, highlighting the dominant role of particle shape in governing segregation behavior.
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