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研究生： 張家耀
Chang, Chia-Yao
論文名稱： 金屬粉末雷射熔融基層製造精密平台系統之氣氛腔體流場分析
Flow analysis of the laminated manufacturing system with laser sintering of metal powder
指導教授： 王偉成
Wang, Wei-Cheng
學位類別： 碩士
Master
系所名稱： 工學院 - 航空太空工程學系
Department of Aeronautics & Astronautics
論文出版年： 2016
畢業學年度： 104
語文別： 英文
論文頁數： 36
中文關鍵詞： 選擇性雷射熔化 、3D列印 、流場均勻度 、實驗流體力學 、計算流體力學
外文關鍵詞： Selective laser melting, 3D printing, flow uniformity, experimental fluid dynamics, computational fluid dynamics
相關次數： 點閱：142  下載：7 
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    • 3D列印技術將顯著減少產品原型的開發時間及成本投資，進而提高產品的質與量，有望成為21世紀的的主流製造技術。而其中之選擇性雷射熔化技術(SLM)乃利用高功率雷射選擇性熔融金屬粉末，於此燒結過程中，金屬顆粒將以隨機彈射之方式運動，並將散射或吸收部份之雷射能量，導致整體製程效果不佳，嚴重影響成品之品質，需由所輸入之惰性氣體進行移除。本研究利用套裝軟體CFD-ACE+之計算流體力學分析流體流經腔體後流場分布之情形並以實驗流體力學之方法進行流場可視化與各截面速度分布之量測，於此交叉驗證下計算流場均勻度，藉由所改變相異組合之吹抽氣口厚度、距地高度及風速配比等結果找出最佳之氣氛腔體吹抽設計條件，創造一風速平穩且均勻之氣流場將金屬粒子順利移除至抽氣端，進而使整體製程品質提升。
    由實驗與模擬結果分析可得，在固定吹抽氣風速條件下，相異組合之吹抽氣口厚度與距地高度將影響整體氣簾流場之風速大小及均勻穩定性。透過流場可視化之實驗觀察，在固定吹氣端流量下，改變抽氣端之流量大小將顯著影響主流流體之初始墜地位置及渦旋產生處，當抽氣流量漸大時，墜地及渦旋效應所造成之損失位置將延後發生，表示整體流場在過程中之動量耗損將明顯地減少，進而使得製程中所產生之金屬粒子能更有效地被帶走。

    In order to improve the flow field quality in the selective laser melting (SLM) process, a blow-to-suction device composed of a trapezoid push nozzle, a working chamber and a suction tunnel was applied to investigate the blow-to-suction velocity profile and the degree of uniformity (DOU) through the working chamber. Various parameters such as the trapezoid push nozzle width, suction tunnel width and nozzle-to-plane distances were examined experimentally and computationally. The hot-wire velocity measurement and smoke flow visualization were used to verify the reliability of the simulation. The investigations with various Reynolds numbers and nozzle/tunnel widths reveal that the momentum exchange between the suction tunnel and push nozzle play a significant role for the flow behavior inside the working chamber.

    中文摘要 i ABSTRACT iii ACKNOWLEDGEMENT iv CONTENTS v LIST OF TABLE vii LIST OF FIGURES viii NOMENCLATURE x 1. Introduction 1 2. Experimental Methods 4 2.1 Experimental Setup 4 2.2 Velocity Measurement 6 2.3 Flow Visualization 7 2.4 Uncertainty Analyses 7 3. Numerical simulation 9 3.1 Methodology 9 3.2 Grid and Boundary Condition 9 3.3 Grid convergence study 10 4. Results and Discussion 15 4.1 Sectional velocity distributions 15 4.1.1 Push nozzle width 16 4.1.2 Suction tunnel width 20 4.1.3 The Nozzle-To-Plane Distances 22 4.2 Flow Visualization 25 4.2.1 The starting part of the Sectional flow patterns with different suction velocity 25 4.2.2 The contacting part of the sectional flow patterns with different suction velocity 28 4.3 The degree of uniformity 31 4.4 The metal powder removal in the optimal design 32 5. Conclusions 34 References 35

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