臺灣博碩士論文加值系統

真空產生器是目前半導體製程與面板搬運等應用之基本配備，因具有體積小、質量輕、真空度高和產生真空迅速的特性，所以在搬運精密、易損或是難搬運之物品有無可比擬的優勢，於自動化生產應用佔有重要位置。本研究針對兩段式真空產生器之相關流場進行數值計算與特性分析，藉由觀察其內部之速度與壓力分佈以探討流場缺失，並據此提出合適改善方案；接著分析不同設計之二段式真空產生器的性能特性，計算評比其吸入流量、空氣消耗量、吸入端最大真空度與能源使用效率等。在檢視真空產生器之整體流場狀態後，發現第一段噴嘴提供流體給第二段噴嘴，故需要輸出穩定且高速低壓之流體，方能在兩個吸入端吸入較多的總流量；故為了提升真空產生器之能源使用效率與真空度，選定第一段漸縮-漸擴噴嘴(Converging-Diverging Nozzle)之喉部直徑與漸擴角進行參數分析，並透過數值模擬評估其成效作優化設計。首先調整噴嘴之喉部直徑，從節能角度找出最佳吸入效率值之噴嘴直徑，接著固定喉部直徑進行噴嘴漸擴部分之角度調整；選定各真空產生器產生30 L/min吸入流量之消耗功率，將之與原始第一段噴嘴(喉部直徑1.2mm、漸擴角14˚)所需消耗功率(277.8 N·m/s)比較，作為判別其能源效率基準。在噴嘴喉部直徑之分析中，可確認喉部直徑0.9mm之消耗功率為216.6 N·m/s，為最佳噴嘴喉部直徑之參數值，相較原始噴嘴喉部直徑之效率提升22%。在找出噴嘴喉部最佳直徑0.9mm後，接著固定此喉部直徑進行其漸擴角度調整，分別縮小與放大漸擴角度進行數值運算比較；其中以漸擴角10˚為最佳噴嘴漸擴角度，其消耗功率為174.0 N·m/s，相較原始噴嘴漸擴角(14˚)之能源使用效率提升19.7%，比原始真空產生器共提升37.4%。
由分析結果得知，若將供給氣壓無限制增加並無法提升其最大真空度，超過特定壓力後最大真空度不增反降、且造成更多能源的損失；而外部吸入端真空度即為實際真空產生器吸入口，此區域為腔體連接外面環境之管路，此真空壓亦是實際應用吸取物件之有效壓力，其值隨供給壓變化之趨勢和最大真空度類似，故若要判別吸力可從此區域之真空壓作為依據。綜合彙整本研究之數值分析結果，得知評估真空產生器之能源效率與真空吸力的性能標準，需依使用者之需求來進行正確取捨，當使用者需要吸力較大(即應用端的真空度高)時，則原始喉部直徑 (1.2mm)噴嘴應為正確選項；若真空度已符合實際作業需求，則應考慮降低真空產生器之能源消耗為主，應選擇小尺寸噴嘴 (如喉部直徑0.8或0.9mm)作為真空產生器之合適設計參數。

This research aims to enhance the performance characteristics of a two-stage vacuum ejector, which is used extensively in delivering the fragile and hard-to-handle products, such as the large LCD board with an extremely small thickness. An integrated effort consisting of the numerical simulation on the flow field and the parametric study on its converging-diverging nozzle is utilized here. At first, a numerical flow visualization is executed to realize its flow pattern and operation principle associated with this vacuum generator. It is demonstrated that the high-pressure utility air enters the de Laval nozzle for accelerating its velocity up to supersonic range, which forms an exceptionally low pressure for serving as the driving force to inhale the ambient air through the first suction inlet. Later, this main jet and the drawing air interact intensely and form the serious recirculation phenomenon within a small region between the 1st nozzle outlet and the inlet of the 2nd nozzle. Subsequently, two streams merge into a fast-moving flow to enter the 2nd nozzle for executing another drawing function in the 2nd suction port. Finally, the main jet with total sucking gas are expelled to the atmosphere through the discharge part of the 2nd nozzle.
Moreover, it is concluded that the de Laval nozzle is responsible to generate the maximum gas speed and the vacuum pressure inside this device. So, the throat diameter and the divergent angle of nozzle are selected to carry out the parametric study for attaining a superior performance. Noticeably, the highest vacuum pressure, energy consumption per unit inhaling flowrate, and the total volume flowrate induced from two suction openings are selected as the important performance indexes to evaluate these ejector designs. As a result, at the same inhaling flow rate 30 L/min, the energy efficiency index of the 1st nozzle with a 0.9mm throat diameter is 433.2 N·m/L, which represents a 22% improvement compared to 555.6 N·m/L of the original 1.2mm throat diameter. Regarding the optimum diverging angle for the de Laval nozzle with a 0.9mm throat diameter, CFD outcomes indicate that an extra 19.7% enhancement on energy efficiency index is obtained by reducing divergent angle of the 1st nozzle from the original 14˚ to 10˚. For all design cases considered here, the available vacuum pressure of vacuum generator enlarges for an increasing pressure source before reaching the peak value. After that point, a slightly decrease on the vacuum pressure is resulted from further increasing the utility pressure, which implies an unnecessary energy waste. Thus, a smaller throat diameter of the de Laval nozzle, say 0.8 or 0.9 mm, is suggested for the energy-saving aspect when the available vacuum pressure is sufficient to meet the application requirement.

目錄
摘要 I
Abstract III
致謝 V
目錄 VI
圖索引 VIII
表索引 XI
符號索引 XIII
第一章 緒論 1
1.1前言 1
1.2文獻回顧 7
1.3.研究動機與分析流程 11
1.3.1研究動機與目的 12
1.3.2研究流程 14
第二章 真空產生器與相關理論介紹 18
2.1真空產生器之介紹 18
2.2氣壓控制系統之控制閥簡介 25
2.2.1方向控制閥 26
2.2.2流量控制閥 30
2.3等熵流在漸縮-漸擴噴嘴之特性 34
第三章 物理模型與數值方法 39
3.1模型介紹 39
3.2數值模型之建立 47
3.3網格建立 48
3.4數值方法 55
3.4.1統御方程式與紊流模型 55
3.4.2統御方程式 56
3.4.3紊流模式 58
3.4.4速度與壓力耦合 61
第四章 原始二段式真空產生器之模擬分析 65
4.1真空產生器之常開狀態的模擬分析 66
4.1.1邊界條件設定 66
4.1.2速度場分析 67
4.2真空產生器之常閉狀態的模擬分析 80
4.2.1邊界條件設定 80
4.2.2壓力場分析 82
4.2.3 P-Q曲線圖與效率探討 86
第五章 第一段噴嘴之參數分析與優化 91
5.1第一段噴嘴之喉部直徑 91
5.1.1穩態流場分析 93
5.1.2 P-Q曲線圖與效率之探討 116
5.2第一段噴嘴的漸擴角度 125
5.2.1穩態流場分析 125
5.2.2 P-Q曲線與效率之探討 153
5.3最大真空度與外界吸入端真空度之物理意涵 159
第六章 結論與建議 170
6.1結論 170
6.1.1原始設計之模擬分析 170
6.1.2第一段噴嘴之設計參數分析 172
6.2建議 177
參考文獻 181

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