臺灣博碩士論文加值系統

流體旋轉機械中，當流體經過軸封時，轉軸兩側流場壓降不同(pressure drop)，產生一徑向作用力(radial force)將轉子推回軸封中心位置，後人稱此現象為Lomakin效應。軸封之動態特性是會影響轉子系統的穩定性，提高系統的穩定性是轉子動力學分析上非常重要的問題。過去研究Lomakin效應對於動態係數影響的分析上，均著重在主勁度係數的影響，且影響Lomakin效應的各個因素也沒有完整的討論。本文特別針對各個因素作一系列討論，影響Lomakin效應的因素可以歸納為下列幾點：軸封幾何外形，軸封間隙與半徑比，軸封表面粗糙度，轉子偏心量，入口壓力流失係數，入口渦流效應，流體特性，如黏滯性、種類。本文利用CFD軟體Fluent來分析Lomakin效應以求得更精準的動態係數，並針對各個因素之影響作一詳細討論。

In fluid rotating machinery, dynamics of rotors is affected by Lomakin effects, which are the radially restoring forces caused by the difference of the pressure drops between the opposite sides of the rotor when the fluid flows through seals. The dynamic characteristics of seals can affect the stability of the rotor systems. Rotor Stability is always an important research issue in rotordynamics. In previous research, the influence of Lomakin effects on the dynamics coefficients of seals were not investigated inclusively. Influence of factors on the Lomakin effect are specially studied in this paper. The factors on Lomakin effects include ratio of seal length and shaft diameter, ratio of seal clearance to shaft radius, surface roughness, eccentricity of the rotor, inlet loss coefficients, inlet preswirl, and fluid properties, such as viscosity and variety. In this paper, the influence of factors on the Lomakin effects and the dynamic coefficients are examined by Fluent, a CFD software.

中文摘要--------------------------------vi
英文摘要--------------------------------vii
致謝------------------------------------viii
目錄------------------------------------x
圖目錄----------------------------------xiii
表目錄----------------------------------xxii
符號表----------------------------------xxiv
第一章 緒論-----------------------------1
1.1前言---------------------------------1
1.2文獻回顧-----------------------------1
1.2.1 bulk flow理論---------------------4
1.2.2 實驗法----------------------------5
1.2.3 CFD數值計算-----------------------5
1.3研究動機與目標-----------------------6
1.4本文大綱-----------------------------7
第二章 研究方法-------------------------10
2.1 理論方法----------------------------10
2.2 Fluent對軸封分析之流程--------------13
2.2.1 軸封之幾何外型與邊界條件設定------13
2.2.2 範例分析結果----------------------15
第三章 環境參數設定及結果驗證-----------25
第四章 幾何因素探討---------------------34
4.1軸封的幾何外形-----------------------34
4.2軸封間隙與半徑比---------------------35
4.3軸封壁面摩擦力-----------------------36
4.4轉子偏心量---------------------------37
4.5小結---------------------------------38
第五章 流體因素探討---------------------57
5.1入口壓力流失係數---------------------57
5.2入口渦流效應-------------------------59
5.3流體黏滯係數-------------------------60
5.4不同流體-----------------------------61
5.5小結---------------------------------63
第六章 結論-----------------------------79
參考文獻--------------------------------83
附錄A Gambit前處理建模範例--------------88
附錄B Fluent求解假設與分析--------------97
附錄C Fluent後處理的觀察----------------108
簡歷------------------------------------114

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