粉粒體與人類日常生活息息相關，但很少為人所察覺，不僅在尖端科技術上扮演關鍵的角色，在一般的化學工業也佔有舉足輕重的地位。大量運用到粉粒體科技的工業除了粉末冶金與鍛造外，還有半導體產業（IC）的後段製程－電子封裝（Electronic packaging），另外還有快速成型技術（RP）也都是以粉粒體為主的新科技。粉體分級技術（Powder classification）廣泛應用在藥品、食品、化工、金屬、橡塑膠類粉末等，可以提高粉粒體的應用領域，粉體分級技術在國外已是相當成熟的一項技術，在國內卻甚少有人對此做更深入的研究。
本研究嘗試藉由氣動力原理，探討離心力式分級機構的各種現象，其原理乃利用葉輪對大小不同的粉粒體施予離心力，並額外提供一表面阻力，藉由兩力的平衡來產生某一範圍的分級。由本研究的結果得知以雷射繞射粒徑分析儀來測量水溶性粉末粒徑時，若該粉末顆粒具沾黏性，會使粉末互相黏結，造成量測粒徑上有很大的差異，需施加外力使粉末分散，才能正確的測量到粉末粒徑。在此吾人新定義一參數稱分級粒度比（Classification size ratio，CSR）：CSR={粗顆粒群組之Dv(10)}/{細顆粒群組之Dv(90)} ，CSR可用來作為粗細顆粒兩群組分隔的程度的指標。CSR>=1時，表示粗細顆粒兩群組有良好的分離程度；CSR<<1時，表示粗細顆粒兩群組的分離程度不良。而實驗結果顯示細顆粒群組平均粒徑隨流體流量增加而上升，因葉輪結構之故，並未隨葉輪轉數增加而明顯下降，若變更背壓較高的細粉回收裝置，則將使細顆粒群組平均粒徑、相對跨度降低，CSR提高。

Powder is associated with human life intimately. Powder technology plays an important role not only in traditional industry, e.g., food industry, powder metallurgy, but also in high-tech oriented regime, e.g., electronic packaging of IC, Rapid Prototyping (RP), precision ceramics, electronic materials, catalyst and biological science.
In this study, powders are classified by centrifugal classifier. The centrifugal force acts on different diameter size powder by blade, and supply another drag force to classify it from centrifugal flow field. It is found that inaccuracy of measurement by laser diffraction particle size analyzer is very serious if powder were agglomerated. It can be corrected during classifying powder by applying additional force.
A new index of “Classification Size Ratio, CSR” is defined as CSR={Dv(10)of Coarse part}/{Dv(90)of Fine Part}. CSR can be used as the judgment of the level of separation between coarse and fine powder. If CSR≧1, it represents the classification to be considerably good to separate into two group of powders; however, if CSR<<1, it represents the poor separation of powder. The experimental results show that the mean diameter size of fine powder will increase while fluid flow rate is increased, but it will not decrease obviously while blade angular velocity is reduced because of blade construction. When the back pressure of the fine powder collector is high, the mean diameter size and relative span factor will be decreased, but CSR will be increased.

1.Asano, K., Funayama, Y., Yatsuzuka, K., and Higashiyama, Y., “Spherical Particle Sorting by Using Droplet Deflection Technology,” J. Electrostatics, Vol. 35, pp. 3-12, 1995.
2.Hamaker, H. C., “The London-Van Der Waals attraction between spherical particles,” Physica IV, No. 10, pp. 1058-1072, 1937.
3.Fortes, A. F., Caldas, P. and Gallo. J. V., “Particle aggregation and the van der Waals forces in gas-solids fluidization,” Powder Technology, Vol. 98, pp. 201-208, 1998.
4.Elghobashi, S. E., “On Predicting Particle-Laden Turbulent Flows,” Applied Scientific Research, Vol. 52, pp. 309-329, 1994.
5.Crowe, C. T., Troutt, T. R. and Chung, J. N., “Numerical Models for Two-Phase Turbulent Flows,” Annual Review of Fluid Mechanics, Vol. 28. 99. 11-43, 1996.
6.Soo, S. L., “Fluid Dynamics of Multiphase System,” Chap 2, Blasidell, Waltham, MA, 1967.
7.Putnam, A., “Integrable Form of Droplet Drag Coefficient,” ARS, J., Vol. 31, pp. 1647-1648, 1961.
8.Wang, Q., Morten, C. M., and Sunil, R De S., “Investigation and simulation of a cross-flow air classifier,” Powder Technology, Vol. 120, pp. 273-280, 2001.
9.Kolaitis, D. I., and Founti, M. A, “Modeling of the gas-particle flow in industrial classification chambers for design optimization,” Powder Technology, Vol. 125, pp. 298-305, 2002.
10.吳昭輝, “以側向風力篩選粉末之數值研究,” 國立成功大學航太所碩士論文，2002。
11.Linoya, K., Gotoh, K. and Higashitani, K., “Powder Technology Handbook,” Marcel Dekker, INC, pp.521-524, 1990.
12.日本粉體工業技術協會、流體分級分科會, “粉體分級技術,”，廣信社。
13.Martin, R., “Introduction to Particle Technology,” John Wiley & Sons Ltd, pp.177-178, 1999.
14.Allen, T. “Particle Size Measurement,” Chapman & Hall, pp. 325-331. 1981.
15.Roldan-Villasana, E. J. Williams, R. A. and Dyakowski, T., “The origin of the fish-hook effect in hydrocyclone separators,” Powder Technology, Vol. 77, pp. 243-250, 1993.
16.Wang, X., Ge, X., Zhao, X. and Wang, Z., “Study on horizontal turbine classification,” Powder Technology, Vol. 102, pp. 166-170, 1999.
17.Wang, X., Ge, X., Zhao, X. and Wang, Z., “A model for performance of the centrifugal countercurrent air classifier,” Powder Technology, Vol. 98, pp. 171-176, 1998.
18.Yamada, Y., Yasuguchi, M. and Iinoya, K., “Effects of Particle Dispersion and circulation Systems on Classification Performance,” Powder Technology, Vol. 50, pp. 275-280, 1987.
19.Timmermann, D. and Schonert, K., “Process equation for centrifugal counter flow classification,” Powder Technology, Vol. 105, pp. 179-185, 1999.
20.Galk, J., Peukert, W. and Krahnen, J., “Industrial classification in a new impeller wheel classifier,” Powder Technology, Vol. 105, pp. 186-189, 1999.
21.Morimoto, H. and Shakouchi, T., “Classification of ultra fine powder by a new pneumatic type classifier,” Powder Technology, Vol. 131, pp. 71-79, 2003.
22.Wedd, M. W., 陳明裕編譯, “Mie Theory and Particle Size Analysis,” Light Scattering, Trekintal corp. Summer 96’ issue, 1996.
23.“雷射繞射粒徑分析儀,” Light Scattering, Trekintal corp. Winter 99’ issue, 1999.
24.Muller, Frank. and Polke, R. F., “From the product and process requirements to the milling facility,” Powder Technology, Vol. 105, pp. 2-13, 1999.
25.秦道堅, “實用高等有機化學,” pp.738-739, 台北商務，民64.
26.呂維明、戴怡德, “粉粒體粒徑量測技術,” 高立圖書，1998.
27.黃坤祥, “粉末冶金學,” 中華民國粉末冶金協會，2001.
28.Lefebvre, H., “Atomization and Sprays,” Hemisphere Publishing Corporation, 1989.
29.Parker, C. R., “Introduction to Aerosol Science,” Macmillan Publishing Corporation, 1984.