存於油膜軸承系統中，流體所引發之不穩定現象已經被研究多年。此研究提議使用可實施最少次實驗之田口法，來評估流體引發不穩定之相關因子的影響程度。在實驗中，配重塊不平衡、油循環堵塞、油壓及油溫被視為控制因子，且區分為兩種級別，並進而決定 直交表。當機械裝置的操作狀況改變，透過機械振動信號的分析可以評估不穩定門檻。結果顯示，配重塊不平衡和油溫是流體引發不穩定的重要因子，且配重塊不平衡有較大之影響。因因子間存在著交互作用，當配重塊不平衡和其他任一因子共同使用，反而會提早引發不穩定。所以對於消除不穩定而言，配重塊不平衡只能單獨作用。因此，提高油溫是最有效增加不穩定門檻之方法。因軸頸速度相關聯之流體周圍平均速度是引起不穩定的關鍵因素，所以透過使用最佳化控制之線性二次調節器注入反漩渦，以減輕且甚至消除在旋轉機械中之油漩，進而增加不穩定的門檻，也是本研究之目標。為了決定啟動控制程序，本研究建立可接受範圍，並利用三個案例來驗證此控制方案之有效性。研究結果顯示，結合可接受範圍之控制方案有能避免旋轉機械中流體引發不穩定之能力。此外，此發展技術可以被適用於其它流體引發不穩定問題，諸如油顫和摩擦等等。;The phenomenon of fluid-induced instability existing in fluid-film bearing systems has been addressed for years. The revolution speed at which the instability onset occurs is called the threshold of instability. The important parameters of the instability threshold are fluid circumferential average velocity ratio and fluid radial stiffness. The study proposes to construct experimentation based on Taguchi method with the least runs of experiment to evaluate the influence of factors on the occurrence of fluid-induced instability. Disk unbalance, oil circulation blocking, oil pressure, and oil temperature classified as control factors with two levels are selected to conduct the experiments. Then, the appropriate orthogonal array L8 is determined. When the operation conditions of machinery change, the threshold of instability can be evaluated through the analysis of machinery vibration signals. Observed from the results, disk unbalance and oil temperature are the significant factors for fluid-induced instability. However, due to interaction between each factors, the instability occurred earlier when disk unbalance and any other instability factors are performed together. Thus, disk unbalance should be dealt with solely for the elimination of instability. As a result, the threshold of instability can be most effectively increased by raising oil temperature. Since the fluid circumferential average velocity associated with journal speed generally is a key factor to cause the instability, thus the research also aims to soothe and even eliminate the occurrence of whirl in rotary machinery by increasing the threshold of instability through the anti-swirl injection using the linear quadratic regulator based optimal control. An acceptance region was established in order to decide starting up the control process. Three case studies were carried out to illustrate the effectiveness of the control scheme. The research results demonstrate that the control scheme incorporating with the acceptance region enables to avoid the occurrence of fluid-induced instability in rotary machinery. Moreover, the developed techniques can also be applied in other fluid-induced instability problems such as whip and rub, etc.
