臺灣博碩士論文加值系統

渦輪機包括噴射引擎及渦輪發電機等，其動葉片都有葉片振動的問題。通常由於顫振(Flutter)，或是強制式響應(Forced Response)所引起的過度振動，都可能造成葉片的損壞(Failure)。葉片設計通常會採用覆環式(Shrouded)，包括葉尖覆環(Tip Shroud)或是葉中覆環(Mid-Span Shroud)，以提升動葉片的結構阻尼(Structural Damping)與強度。目前對於渦輪機覆環式動葉片之顫振或強制式響應現象，缺乏完整系統之研究方法，必須以過去經驗來作為渦輪機覆環式動葉片設計的依據。
本研究主要將針對渦輪機覆環式動葉片的顫振現象，建立一套完整系統之研究方法，來探討覆環式動葉片產生顫振的主要機制。首先要有葉片的結構動態特性，包括葉片自然頻率以及模態等，通常是以實驗及有限元素方法作量測與分析。接著結合葉片表面超音速，穿音速，次音速等流場來計算出由於結構運動所產生的非穩定氣動力負荷。由於覆環式的動葉片設計造成整體轉子結構呈現系統模態運動(System Mode)，必須採用週期對稱方法(Cyclic Symmetry)，再結合顫振分析系統的模式分析程式(Modal analysis)，俾能計算出整個覆環式動葉片系統之氣動力阻尼(Aero Damping)，以決定其顫振特性。
本研究分析的實例包括有電廠汽渦輪機及飛機引擎風扇的覆環式動葉片。結果顯示葉片的振動模態是影響顫振特性的重要因素，對於振動模態較複雜的模態，週期對稱方法可提供一個客觀且省時的答案，不失為一個有效的分析工具。相對的，傳統的單一葉片法無法提供足夠判斷的結果，甚至可能導致錯誤的估計。

A frequent cause of turbomachinery rotor blade failure, including jet engines, aircraft engines and turbogenerators, is excessive vibration due to flutter or forced response. One method for dealing with this problem is to increase blade structural damping, using either tip or mid-span shroud design. Unfortunately, most existing aeroelastic analyses deal with blade alone model, which can not be used for system mode analysis. Therefore, judgements based on past experience are used to determine the acceptability of a shrouded blade design. A system approach analysis will be developed to predict shrouded blade flutter. This analysis will provide a system approach, over and above the standard blade alone approach, for predicting potential aeroelastic problems. Using the blade natural frequencies and mode shapes from both measurements and a finite element model, the unsteady aerodynamic forces of the system mode will be calculated using the blade surface supersonic, transonic, and subsonic flow field. A system flutter analysis will then be performed using a modal solution to determine the stability of the system. Besides using the experimental data to verify the finite element blade model, a non-shrouded blade flutter analysis will be used to verify the system mode flutter analysis. Also, we will use this method to study the major mechanism causing shrouded rotor blade to flutter in some specific modes including bending and torsion modes. Shrouded rotor blade design has been widely used in fans, compressors, and turbines. The proposed research method can remedy the current deficiency in shrouded rotor blade design and also can provide guidance for shrouded blade maintenance and life management.

摘 要 I
目 錄 III
表目錄 VI
圖目錄 VII
符號說明 XI
第一章 緒論 1
1.1 研究背景 1
1.2 文獻回顧 2
1.2.1顫振與強制響應之簡介 2
1.2.2 葉片及轉子的結構振動 4
1.2.3 空氣彈性力學（aeroelasticity） 5
1.2.4 顫振（flutter） 7
1.2.5 非穩態氣動力模型 8
1.2.6 氣彈模型 10
1.2.7 振動模態與週期對稱 12
1.3 研究目的 12
第二章 分析系統與研究方法 13
2.1 基本理論 13
2.2 分析程式 16
2.2.1 程式簡介 16
2.2.2 葉片結構模型建立 17
2.2.3 顫振分析的流程 18
2.3 研究方法 18
2.4 與次音速2維模型之比較 20
2.5 週期對稱模型之驗證 21
第三章 電廠渦輪機葉片之顫振分析 22
3.1 六片單組模型的單一葉片方法 22
3.2 六片單組模型的週期對稱分析 25
3.3 完整60片模型的顫振分析 26
3.4 電廠汽渦輪機葉片之討論 28
第四章 飛機引擎風扇葉片之顫振分析 30
4.1 中間覆環式風扇葉片（Fan Rotor 1） 30
4.2 葉尖覆環式風扇葉片（Fan Rotor 2） 31
4.3 震波位置的影響 32
第五章 週期對稱模型之研究 33
5.1 相反的分析結果 33
5.2 Bending與Torsion結合之差異 34
5.3 互換實部與虛部的影響 35
第六章 結 論 37
參考文獻 39

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