近年來無油高速轉子系統對於符合環保之發電系統至為重要，故而在系 統上均採用氣體箔片軸承以支撐高速轉子是關鍵核心技術。這類軸承在運轉過程無須使用潤滑油及相關輔助系統，主要研究是源起於二十世紀之70年代，而後應用於航空業之輔助動力裝置及空氣循環機。這類軸承技術發展至今日，對於軸承運轉之動態工作特性尚未完全解析；舉例而言，軸承內部氣膜壓力及溫度分佈情形，甚而於各種工作條件能有效進行軸承之熱管理方法，都是待深入分析探討。本論文先參酌文獻回顧之有限設計及運轉參數資料，在確定流程後進行全面性分析及研究，對這類型軸承之設計及運轉相關理論深入理解，發展出先進熱管理方式，期望實現軸承動態性能之最佳化設計。本論文提出採用基於多物理場三維電腦輔助有限元素分析法之暫態數值分析模型， 經由計算流體力學與結構力學之聯合分析模組之流固耦合方式， 建構出模擬軸向及徑向之氣體箔片軸承之動態運行數值模型。以不同邊界及起始條件輸入模型，並持續計算分析達到準穩態情形，從分析過程之各項儲存物理量，可完整探討此軸承之動態特性。因為採用商用套裝軟體進行分析模擬，必須簡化各項複雜物理現象以提升計算效率，故以薄板理論簡化箔片結構並將其設定為均質線性彈性體，便於以設計參數分析及調配完整軸承薄片及轉子之運轉動態特性。在採用實驗設計進行驗證徑向及軸向軸承之分析後，再將實驗結果與文獻發表之數據交叉比對，本論文建構之分析方式對探討氣體箔片軸承之設計及動態運轉特性確為有效方法，並對這類軸承系統之設計及調配運轉參數具可直接應用，並拓展相關高速氣動領域之未來研究方向。

In recent years, oil-free high-speed rotor systems are considered crucial for eco-friendly power generation systems, contributing to the progress of gas foil bearings into an essential technology. These bearings eliminate the needs for lubricating oil and related components during operation. The development of relevant technology gained momentum in the 1970s, especially in aeronautical applications as auxiliary power units and air cycle machines. However, pertinent operational characteristics of these bearings remain mysterious in many ways, for example, the distribution of pressure and temperature field in the thin gas film and the efficient methods of thermal management during various operating conditions. Based on the literatures review relevant to the finite element method and design parameters, the dissertation determines to conduct thorough and comprehensive analysis of the bearings. Furthermore, the advanced thermal management method could also be theorized and modelled after the completion of dynamic analysis. Initially, a comprehensive three-dimensional analysis model employing the fluid-structure interactive finite element method is introduced for the simulation of the operational performance of gas foil bearings. The simulation model is established by cooperating the computational fluid dynamics with the transient mechanical stress calculation via data-transferring co-simulation. With this simulation model, it is possible to examine the working characteristics and performance of the bearing system by conducting the timewise transient analysis in steps until the quasi steady state is reached. As a result, the details in the simulation depict both the physical phenomena and the working characteristics of the bearings. To simplify the simulation process by using the commercial CAE program, the foil structure of the bearings can be treated as a homogeneous solid material according to the plate and shell theory in elasticity. Therefore, the analysis and comparisons of the operational properties among various design of gas foil bearings can illustrate the operational characteristics. To verify the simulated results from the simulation model, comprehensive insights of the dynamic operational characteristics of the gas foil bearings are significant. Hence, the simulation model demonstrates to possibilities in seeking for deeper understanding of the design parameters and operational characteristics of the gas foil bearings. In conclusion, through the in-house experimental measurements on both radial and thrust gas foil bearings and data from the literatures, the verification of the dynamic efficacy of the simulation model have been confirmed. As a result, it is evident that a digital twin analysis model for gas foil bearing systems is very promising in the future development. This innovative study provides notable potential in enhancing fundamental basic knowledge, comprehending theory and conducting analysis of the bearing systems; hence, similar high speed rational aerodynamic studies are explorable in the future.

TABLE OF CONTENTS
摘 要
ABSTRACT
ACKNOWLEDGEMENT
TABLE OF CONTENTS………………………………………………………Ⅰ
LIST OF TABLES AND FIGURES…………………………………………Ⅲ
NOMENCLATURES AND NOTATIONS…………………………………Ⅶ
CHAPTER 1 INTRODUCTION TO GAS FOIL BEARINGS…………………1
1.1 Background of Study and Motivation ……………………………………1
1.2 Literature Review ………………………………………………………4
1.3 Objectives of Study ……………………………………………………18
CHAPTER 2 HYDRODYNAMICS AND SOLID ELASTICITY ……………23
2.1 Hydrodynamics in Lubircation Theory ………………………………23
2.2 Plate and Shell Elasticity in Solid Mechanics …………………………25
2.3 Governing Equations in Radial Operation of GFBs ……………………27
2.4 Concluding Remarks …………………………………………………30
CHAPTER 3 HYDRODYNAMIC MODEL IN CAE SIMULATION………33
3.1 CAE Flow Simulation and Geometric Model of GFBs ………………33
3.1.1 Gas Properties and Boundary Conditions ………………………34
3.2 Meshing of Elements and Bench Mark Simulations ……………………36
3.3 Basic Geometric Model of GFTBs ……………………………………39
3.4 Model Meshing and Boundary Conditions ……………………………42
3.5 Experimental Verifications of the GRTBs ……………………………44
CHAPTER 4 CAE MODEL WITH FLUID-STRUCTURE INTERACTIONS …………………………………………………………………………………54
4.1 Interactions of Fluid and Structure in Radial Operation GFBs …………59
4.2 Interactions of Fluid and Structure in Axial Operation GFTBs ………59
4.3 Concluding Remarks ……………………………………………………62
CHAPTER 5 FULL-MODEL CAE TRANSIENT SIMULATION …………69
5.1 Simulation Cases for Radial Operation GFBs …………………………69
5.2 Simulation Cases for Axial Operation GFTBs …………………………74
5.3 Spring-damper Case for Clamped-Rotor Axial Operation of GFTBs …79
CHAPTER 6 CONCLUSIONS AND FUTURE WORKS …………………90
6.1 Conclusions ……………………………………………………………90
6.2 Future Works ………………………………………………………92
BIBLIOGRAPHY……………………………………………………………94

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