本論文利用商業套裝軟體CFD-ACE+建立熱鍍鋅產線之氣刀三維模型，並透過優化內部氣刀結構，以改善整體熱鍍鋅產線之流場與壓力分布，減少鍍鋅鋼板表面漣漪痕之產生，提升鍍鋅鋼板的品質。
本論文在探討熱鍍鋅產線目前所需改善的方向，然後建立計算模型與完成邊界條件設定，並將此熱鍍鋅產線氣刀模組作為基礎建模並將其延伸，旨在研究探討在改變內部結構以及穩壓板孔洞之數量與大小下，對於鍍鋅鋼板衝擊壓力的分布影響。首先計算此氣刀流場模型之衝擊壓力與速度並與文獻做比較，得到一個符合實際情形的基礎解之後，嘗試四種改善之設計方案。在[方案一]中將整體氣刀組的氣室中再額外加入一個穩壓板，並與基礎解之結論相比，探討多加一塊穩壓板之效果與其必要性；在[方案二]中將氣刀前端非對稱之結構改為對稱，期望對稱的前段結構可以比起基礎解有更均勻的壓力分布；[方案三]則是將氣刀模組中穩壓板孔洞之數量與大小進行調整，以求在內部可以獲得更加均勻的壓力與流場。進行了以上三個方案之後發現添加額外的穩壓板以及改變內部之幾何結構對於整體的壓力分布是影響不大的，因此可以推斷漣漪痕的產生主要原因在於隨時間變化所產生的壓力變動。因此在[方案四]中會根據[方案三]中改變孔洞之數量與大小的穩壓板進行暫態模擬，從各式板型中找尋最適合者，使得其在一給予的壓力週期函數下可以有更加優秀的穩壓效果。

The objective of this thesis is to redesign the internal structure of air-knife system to avoid ripple marks on the surface of hot dip metallic coating plates. The model of air-knife system of this work will be simulated and computed with the commercial CFD software, CFD-ACE+.
Four designs will be considered in this thesis to redesign the air-knife system. In Design 1, an additional pressure equalizer was added to the cylinder of the air-knife system, and the computed results will be compared with those of the original design to justify the necessity of adding an additional pressure equalizer. In Design 2, an asymmetric structure in the front of the air knife will be modified to a symmetric structure to provide more uniform pressure distribution in the air knife outlet. In Design 3, the number and size of the holes of pressure equalizer in the air-knife model will be adjusted to obtain more uniform pressure distribution. After the observation of the results of the above three steady-state condition designs, it was found that adding an additional pressure equalizer and changing the internal structure has limited effects on the overall pressure distribution. Therefore, it can be concluded that the main reason for the ripple marks could be the pressure change over time, i.e. the transient variation of pressure should be considered. In Design 4, the modified pressure equalizer in Design 4 will be subjected to a time-dependent pressure source, and the most suitable pressure equalizer will be selected to obtain most stable pressure distribution, i.e. the role of a pressure equalizer should be replaced by a pressure stabilizer.

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