使用電磁致動器消除流體引發不穩定及乾颤之研究

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研究生：	范振朝 Chen-chao Fan
論文名稱：	使用電磁致動器消除流體引發不穩定及乾颤之研究 Study of Eliminating Fluid-Induced Instability and Dry Whip Using Electromagnetic Actuators
指導教授：	潘敏俊 Min-chun Pan
口試委員:
學位類別：	博士 Doctor
系所名稱：	工學院 - 機械工程學系 Department of Mechanical Engineering
畢業學年度：	99
語文別：	英文
論文頁數：	138
中文關鍵詞：	摩擦、流體顫、流體漩、流體引發的不穩定、乾顫
外文關鍵詞：	Fluid whirl, Fluid whip, Rub, Fluid-induced instability, Dry whip
相關次數：	點閱：11 下載：0
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消除存在於旋轉機械中的流體膜軸承的流體漩、流體颤及乾颤等不穩定，就安全和穩定操作而言是相當重要的。當平滑而圓柱狀的動壓軸承處在輕負載的狀況，由於轉子對重力作用之徑向負載，此時軸承中的軸頸可能移動到低偏心比，且軸承內部完全充滿潤滑油。當這種情況發生時，它可能觸發流體引發的不穩定問題。這個研究使用一個回授控制系統的電磁致動器去處理這類不穩定。此致動器可以被當作一個變動勁度的產生器。裝設在靠近旋轉機器的流體膜軸承處的致動器，用並聯結構結合流體膜軸承提供較高的勁度以消除流體引發的流體漩不穩定問題；裝設在靠近旋轉機器的軸中間處的致動器，用並聯結構結合軸勁度提供較高的勁度以消除流體引發的流體颤不穩定問題。致動器原是不動作的，直到遭遇流體引發的不穩定狀況時才動作。當不穩定發生，致動器將結合流體膜軸承或軸勁度去穩定旋轉機器。就致動器而言，藉由應用比例和微分控制當作控制演算法，改變致動器的控制電流利於提供合適的驅動力。比例增益導致力量增加，當作位移的函數，它的功用是模擬勁度。微分增益導致力量增加，當作速度的函數，它的功用是模擬阻尼。更進一步，使用彈簧模型以估算系統所需的勁度，進而增強系統和提升不穩定的門檻。在實驗轉子裝置模型基礎上，提議的方法結合根軌跡並以MATLAB®軟體去模擬轉子系統的勁度及阻尼之穩定狀態。實驗結果呈現旋轉機器的不穩定可以有效地被移除。所提出的技術也可以用來診斷配備有流體膜軸承的旋轉機器中所發生的摩擦和流體引發的不穩定問題。

Elimination of instabilities existing in rotating mechinery, including fluid whirl, fluid whip and dry whip, is imperative for safe and stable operation of rotating machines with journal bearings. When the plain cylindrical journal bearing in rotating machinery is lightly loaded, perhaps due to radial loads on the rotor that act against gravity, the shaft journal can move to low eccentricity ratios, and the bearing can become fully flooded. When this happens, it can trigger fluid-induced instability. This study develops an electromagnetic actuator with a feedback control system to tackle the kinds of instabilities. The actuator can be used as a generator of variable stiffness. The actuator mounted near the fluid-film bearing at a rotating machine incorporates the fluid-film bearing in parallel configuration to provide higher stiffness for eliminating fluid-induced whirl instability, and it mounted near mid-span at a rotating machine incorporates shaft in parallel configuration to provide higher stiffness for eliminating fluid-induced whip instability. The actuator does not act until the system encounters the fluid-induced instability. When instability occurs, the actuator will be actuated and combined with the fluid-film bearing or shaft stiffnesses to stabilize the rotating machine. For the actuator, favorable force of actuation is reached by changing the control current in the actuator applying the proportional and derivative controls as control algorithm. The proportional gain causes the force to increase as a function of displacements; its function simulates stiffness. The derivative gain causes the force to increase as a function of velocities; its function simulates damping. Moreover, a spring model is used to estimate the stiffness the system needs to stiffen the system and raise the threshold of instability. The proposed method combining the root locus plot is based on an experimental rotor rig model, as well as using MATLAB® for simulation. Experimental results demonstrate that the instability of the rotating machine can be removed effectively. The proposed technique can also be used to diagnose rub and fluid-induced instability existing in this kind of rotating machines.

摘 要	I
Abstract	II
誌 謝	IV
Contents	V
List of Figures	VIII
List of Tables	X
Nomenclatures	XI
Chapter 1 Introduction	1
1 Research Background and Motivation	1
2 Literature Review	3
3 Scope of Work	8
4 Thesis Outline	9
Chapter 2 Mathematical Modeling of Physical Systems	12
1 Preface	12
1.1 Types of Bearings	12
1.2 Self-Excited Vibration	14
1.3 Difference between Fluid Whirl and Fluid Whip	16
1.4 Conditions of Determining Stability	17
1.5 Threshold of Instability and Nonsynchronous Dynamic Stiffness	20
1.6 Methods of Eliminating Fluid-Induced Instability	24
1.7 Partial Rub	26
1.8 Full Annular Rub	28
1.9 Difference between Fluid-Induced Instability and Rub	29
2 Mathematical Models	31
2.1 Fluid Force Model	31
2.2 Rotor Model	33
2.3 Electromagnetic Actuator Model	36
2.3.1 Method of Determining Stability of PD Controllers	40
2.4 Rotor-Bearing-Seal-Electromagnetic Actuator Model	42
2.4.1 Rotor-Bearing Model	42
2.4.2 Rotor-Bearing-Seal-Electromagnetic Actuator Model	44
2.5 Spring Model	47
2.5.1 Spring Model for Fluid Whirl and Fluid Whip	47
2.5.2 Spring Model for Coexistence of Fluid Whip and Dry whip	49
Chapter 3 Experimental Setup and Procedure	52
1 Experimental Rotor Rig	52
1.1 Experimental Setup for Fluid Whirl and Fluid Whip	52
1.2 Experimental Setup for Fluid-Induced Instability and Dry Whip	54
2 Flow Chart for Eliminating Fluid Whirl and Fluid Whip and Dry Whip Instability	56
3 Control Strategy for EA	57
4 Elimination Procedure for Fluid Whirl and Fluid Whip and Dry Whip Instability	59
4.1 Elimination Procedure	59
4.2 Method of Determining M, λ, D and K of Rotor Systems	60
5 Design Example	62
5.1 Design Example for Fluid Whirl	62
5.2 Design Example for Fluid Whip	65
5.3 Design Example for Fluid Whip and Dry Whip	67
5.3.1 Criterion for Eliminating Coexistence of Fluid Whip and Dry Whip	67
5.3.2 Design Example for Fluid Whip and Dry Whip	68
Chapter 4 Experimental Results and Discussions	72
1 Experimental Results and Discussions of Fluid Whirl	72
1.1 Observed Vibration Phenomena without Control	72
1.2 Observed Vibration Phenomena with Control	74
1.3 Stability Analysis	76
2 Experimental Results and Discussions of Fluid Whip	77
2.1 Observed Vibration Phenomena without Control	77
2.1.1 Spectrum Cascade and Orbit Plots	77
2.1.2 Spectrum Cascade and Spectrum Plots	79
2.2 Observed Vibration Phenomena with Control	80
2.2.1 Spectrum Cascade and Orbit plots	80
2.2.2 Spectrum Cascade and Spectrum Plots	82
2.3 Stability Analysis	83
3 Experimental Results and Discussion of Coexistence of Fluid Whip and Dry Whip	84
3.1 Observed Vibration Phenomena without a Seal and Control	84
3.2 Observed Vibration Phenomena with a Seal and without Control	87
3.3 Observed Vibration Phenomena under Control	90
3.4 Stability Analysis	92
Chapter 5 Conclusions and Future Works	94
1 Conclusions	94
2 Future Works	96
References	98
Appendix 1 Derivation of Fluid Force	106
Appendix 2 Couette Flow	107
Appendix 3 Orbit and Average Shaft Centerline Plot	111
Appendix 4 Full Spectrum Plot	113
Appendix 5 Derivation of Eqs. (2.43) and (2.44)	116
Appendix 6 Derivation of Eq. (2.50)	118
Appendix 7 Schematic Diagram of PD Controllers and Current Drivers	119
Author Resume and Publication Work	120

                                

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