【摘要】：隨著旋轉機械向著高速、高效、大跨距、大功率方向的發(fā)展，浮動環(huán)密封兩側承受的壓差增大，使得浮動環(huán)密封-轉子系統(tǒng)的非線性動力學特性日益凸顯。傳統(tǒng)的浮動環(huán)密封研究中通常采用線性化的小擾動理論進行分析和設計，其不能很好的描述系統(tǒng)的非線性特性，因而具有一定的應用局限性。因此建立浮動環(huán)密封的非線性油膜力模型對于浮動環(huán)密封-轉子系統(tǒng)的非線性動力學特性分析具有重要意義。針對上述問題，本文對浮動環(huán)的結構、工作原理及其受力情況進行了研究，建立浮動環(huán)密封非線性油膜力近似解析模型，應用該模型對浮動環(huán)密封-汽輪機轉子系統(tǒng)的非線性動力學特性進行數值仿真，，主要研究內容如下： (1)基于小間隙油膜潤滑雷諾方程，采用類似于短軸承模型假設，考慮浮動環(huán)兩端的壓力邊界條件和間隙入口的流體Lomakin效應，建立了浮動環(huán)非線性油膜力模型，并對浮動環(huán)壓力分布及浮動環(huán)靜態(tài)特性進行了數值仿真。 (2)建立了浮動環(huán)流動的三維模型，在此基礎之上對油槽浮動環(huán)間隙內的流場進行數值仿真研究，分析了浮動環(huán)的中間周向油槽幾何尺寸及浮動環(huán)兩端壓差對油槽內的壓力分布的影響；數值仿真研究了浮動環(huán)偏心率及油槽對浮動環(huán)泄漏量的影響規(guī)律。研究表明：浮動環(huán)的泄漏量隨著偏心率的增加而增大，而中間周向油槽能減小浮動環(huán)的泄漏量，且在保持油槽的深度或寬度不變時，隨著油槽深寬比的增加，浮動環(huán)的泄漏量呈逐漸減小的趨勢。 (3)基于建立的浮動環(huán)油膜力模型的基礎之上，結合有限元理論建立了浮動環(huán)密封-汽輪機轉子系統(tǒng)的動力學模型并對其數值仿真研究，獲得不同軸承支承剛度下汽輪機轉子的臨界轉速、模態(tài)振型及動力學響應，分析了不同軸承支承剛度下浮動環(huán)油膜力對轉子臨界轉速和穩(wěn)定性的影響。 (4)基于已建立的浮動環(huán)密封-轉子系統(tǒng)的動力學模型，數值仿真研究了浮動環(huán)的結構參數(長徑比、間隙比、潤滑油粘度、中間周向油槽的幾何尺寸)和浮動環(huán)兩端壓差對浮動環(huán)密封-轉子系統(tǒng)的動力學響應的影響，分析了浮動環(huán)密封-轉子系統(tǒng)的穩(wěn)定性隨各影響因素的變化規(guī)律。研究表明，適當的減小浮動環(huán)的長徑比、潤滑油粘度或增加間隙比、兩端壓差會提高浮動環(huán)密封-汽輪機轉子系統(tǒng)的穩(wěn)定性；在浮動環(huán)中間開設周向油槽能較大幅度提高浮動環(huán)密封-汽輪機轉子系統(tǒng)的穩(wěn)定性，同時隨著油槽寬度的增加，系統(tǒng)的穩(wěn)定性逐漸提高。
[Abstract]:With the development of rotating machinery in the direction of high speed, high efficiency, long span and high power, the pressure difference between the two sides of the floating ring seal increases, which makes the nonlinear dynamic characteristics of the floating ring seal rotor system more and more prominent. In the traditional research of floating ring seal, the linearized small disturbance theory is usually used to analyze and design, which can not well describe the nonlinear characteristics of the system, so it has certain application limitations. Therefore, the establishment of a nonlinear oil film force model for the floating ring seal is of great significance for the analysis of the nonlinear dynamic characteristics of the floating ring seal rotor system. In view of the above problems, the structure, working principle and stress of the floating ring are studied in this paper, and the approximate analytical model of the nonlinear oil film force of the floating ring seal is established. The nonlinear dynamic characteristics of floating ring seal turbine rotor system are numerically simulated by this model. The main research contents are as follows: (1) based on the Reynolds equation of small clearance oil film lubrication, the assumption similar to that of short bearing model is adopted. Considering the pressure boundary conditions at the two ends of the floating ring and the fluid Lomakin effect at the gap inlet, a nonlinear oil film force model of the floating ring is established, and the pressure distribution of the floating ring and the static characteristics of the floating ring are numerically simulated. (2) the three-dimensional model of floating ring flow is established, and the numerical simulation of the flow field in the gap of the floating ring of the oil tank is carried out on the basis of the model. The influence of the geometry size of the middle circumferential oil tank and the pressure difference between the two ends of the floating ring on the pressure distribution in the oil tank is analyzed. The influence of the eccentricity of the floating ring and the oil tank on the leakage of the floating ring is studied numerically. The results show that the leakage of the floating ring increases with the increase of the eccentricity, and the leakage of the floating ring can be reduced by the middle circumferential oil tank, and when the depth or width of the oil tank is kept constant, the ratio of depth to width of the oil tank increases. The leakage of the floating ring is decreasing gradually. (3) based on the oil film force model of floating ring, the dynamic model of floating ring seal turbine rotor system is established with finite element theory and its numerical simulation is studied. The critical speed modal mode and dynamic response of turbine rotor under different bearing stiffness are obtained. The influence of floating ring oil film force on the critical speed and stability of the rotor under different bearing supporting stiffness is analyzed. (4) based on the established dynamic model of floating ring seal rotor system, the structural parameters (aspect ratio, clearance ratio, lubricating oil viscosity) of floating ring are numerically simulated. The effects of the geometric dimension of the middle circumferential oil groove) and the pressure difference between the two ends of the floating ring on the dynamic response of the floating ring seal rotor system are analyzed. The variation of the stability of the floating ring seal rotor system with the influence factors is analyzed. The results show that the stability of the rotor system of the floating ring can be improved by decreasing the ratio of length to diameter of the floating ring, increasing the viscosity of the lubricating oil or increasing the clearance ratio, and the pressure difference between the two ends will improve the stability of the rotor system of the floating ring. Setting a circumferential oil groove in the middle of the floating ring can greatly improve the stability of the rotor system of the floating ring seal steam turbine. At the same time, the stability of the system increases gradually with the increase of the width of the oil slot.
【學位授予單位】：哈爾濱工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：TH133

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