氣靜壓軸承係利用加壓空氣填充轉軸與軸承的間隙，提供主軸適當的潤滑與阻尼，具有取得成本低、磨擦小、不易發熱、潔淨、高旋轉精度、運轉平穩、器材損耗率低、壽命長等優點，因此已應用於超精密的航太、半導體、工具機與測量儀器等領域。其中，小孔節流和全多孔質材料節流是氣靜壓軸承主要的節流形式，而局部多孔質材料節流是結合前兩者所產生的新節流方式，具有結構簡單、剛性強的特點，唯針對此種節流的研究較少，故存在許多探討的空間，本研究將針對「局部多孔質軸頸軸承」和「局部多孔質止推軸承」之性能進行探討，供日後在設計研發氣靜壓軸承時之參考依據。本研究主要利用計算流體力學軟體Fluent進行分析，在忽略熱傳與重力效應的前提下，建立流體模型去分析軸承間隙內之氣膜壓力分佈，同時為了確保網格密度而利用模型的可分割性，分割出同樣也足以表達其物理現象的局部模型，再調整各項設計參數以探討其對軸承之各性能之影響。
　　在「軸頸軸承」的研究中，調整的參數為主軸偏心距離、進氣壓力、進氣排間距和排數、柱塞個數與分佈。而在「止推軸承」的研究中，調整的參數為進氣壓力和柱塞個數與分佈。模擬結果顯示，隨著主軸轉速上升，主軸在承受徑向負載時所產生的偏心將越偏離負載方向；當進氣壓力愈大，主軸剛性雖然會增加，但效益卻會遞減，同時軸承的阻尼均勻性將降低，可能導致主軸的不穩定性增加；當進氣排的間距較遠時，則能拉大軸向間距以增加氣膜高壓涵蓋面積，進而提升軸承負載，而增加進氣排的數量雖也能提升負載能力，但效果不如前者明顯，主要在於給予更穩定均勻之阻尼，而增加單列進氣排上之柱塞個數也具有類似效果，但影響範圍不同，其主要功用在於令軸承在圓周方向的阻尼更加均勻。

　　Air bearings are bearings that use a thin film of pressurized air to provide an extremely-low-friction interface inside the gap between spindle and bearing. Because these two surfaces do not contact, air bearings can prevent the traditional bearing-related problems of friction, wear, and lubricant handling, and offer key advantages in precision positioning; thus air bearings are being utilized in precision machinery tools recently. This study utilizes the commercial CFD software Fluent to solve the compressible, three dimensional Navier-Stokes equations for calculating the fluid pressure inside the air bearing, and investigates the performances of the porous-media aerostatic journal and thrust bearings via the flow simulation. Later, an in-depth parametric study is executed systematically to evaluate the corresponding effects on bearing characteristics, such as the pressure distribution, the average surface pressure and the stiffness on spindle. The important parameters considered here include the rotational speed of spindle, the eccentric ratio, the input air pressure, the separated distance and the number of porous inserts in both axial and circumferential directions.
　　As a result, numerical simulation indicates that the increase of loading capacity is proportional to the eccentric angle, which occurs frequently under a high-speed spindle rotation, say 60,000 rpm. Also, the average pressure on spindle surface is a proportional function of the input air pressure, and the damping uniformity of axis is inversely proportional to the inlet air pressure. In addition, the average pressure on spindle surface becomes bigger when the porous inserts are separated further in axial direction. However, the porous insert number in both circumferential and axial direction has minor effect on the average pressure of spindle surface. In fact, increasing insert number only enhances the stable and uniform damping on the spindle. In summary, this numerical investigation considers many parameters for enhancing the pressure and the stiffness of thrust bearing and journal bearing. Also, the physical phenomenon of dynamic-pressure effect inside the porous bearing is analyzed comprehensively for the high-speed spindle case, which can serve as a vital design reference for many engineering applications.

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