【作者】 杨利花；

【导师】 虞烈； 刘恒；

【作者基本信息】 西安交通大学 ， 机械工程， 2009， 博士

【摘要】 动压气体轴承因其优于油润滑轴承的优良性能被广泛应用于涡轮膨胀机等高速旋转机械中,对于这类轴承的静、动态性能以及相应转子系统的动力学行为进行系统的实验和理论研究,是轴承设计和使用的关键,对提高轴承性能和扩大其应用范围有重要意义。本文给出了可倾瓦动压气体轴承静、动态性能的计算方法,以及可倾瓦轴承-转子系统动力学行为的分析方法,并在此基础上率先建立了引入压电作动器和PID反馈控制系统的可倾瓦轴承-转子系统振动的主动控制模型,实现了对系统不平衡响应的最优控制。此外,本文还结合国家“863”项目,建立实验台对弹性箔片动压气体轴承的静态和动态性能进行了实验研究。本文的主要研究内容为:1.在采用有限元法迭代求解动压气体润滑静态Reynolds方程的基础上,计算了可倾瓦动压气体轴承的静态性能并进行了有限元仿真,详细讨论了轴承预负荷、压缩数等轴承参数对轴承静态性能的影响。2.采用偏导数法在复数域内求解动压气体润滑的动态Reynolds方程,给出了轴瓦和轴颈同频扰动时可倾瓦轴承的动态刚度和阻尼系数的两种计算方法,通过计算结果的对比说明了这两种计算方法的有效性。借助数值仿真结果,讨论了轴承参数对轴承动态系数的影响,并首次全面解释了轴颈和轴瓦的动态扰动频率对可倾瓦动压气体轴承的动态刚度和阻尼系数的影响,以及它们各自在轴承动态系数中所起的作用。3.应用极限理论,计算了扰动频率Ω→0+和Ω→+∞时可倾瓦轴承的动态刚度和阻尼系数的极限值,提供了一种轴承静态刚度和阻尼系数的计算方法,使得在全频率范围内研究可倾瓦动压气体轴承的动态性能成为可能。4.依据运动方程中是否包含轴瓦的摆动自由度,建立了可倾瓦轴承-柔性转子系统的两种动力学计算模型,并在考虑轴承动态系数的频率效应的前提下,根据求得的系统特征值分析了转子系统的稳定性,完善了可倾瓦动压气体轴承-转子系统的稳定性分析。结果表明,这两种计算模型得到的系统特征值以及对系统稳定性的分析结果是一致的。5.通过引入压电作动器和PID反馈控制系统,率先建立了可倾瓦轴承-转子系统振动的主动控制模型,应用最优控制理论得出了系统最优反馈的电压-位移控制律,实现了转子系统不平衡响应的有效抑制,为进一步改善可倾瓦轴承-转子系统的稳定性提供了理论基础。6.搭建了弹性箔片动压气体轴承的多功能测试实验台,给出了弹性箔片动压气体轴承静、动态性能的测试方法。将摩擦力矩法和位移响应频谱法相结合,较精确地识别出了径向轴承的起飞转速,采用最小二乘法在时域内计算了径向轴承的动态刚度和阻尼系数,重点分析了激振频率对轴承动态系数的影响,并应用位移响应频谱法解决了弹性箔片止推轴承起飞转速实验识别的难题。更多还原

【Abstract】 The aerodynamic bearings are successfully used in high speed rotating machines such as turbo expanders because of their excellent performance. The systematically experimental and theoretical researches on the static and dynamic performance of this type of bearings and the dynamic analysis of the related rotor systems are very important for the bearing design and application, especially for advancing the performance and widening the application of the bearings. This dissertation presents the theory and the numerical calculation method for predicting the performance of the aerodynamic tilting-pad bearing and related rotor systems. And it firstly builds an actively control model for controlling the vibration of the rotor systems supported by tilting-pad gas bearings based on applying the piezo-electric actuators and PID feedback control systems. Furthermore, a test rig is established to predict the static and dynamic performance of the compliant foil gas bearings. The main contents of this dissertation are listed as follows:1. The compressible gas-lubricated static Reynolds equation is iteratively solved by means of the finite element method for calculating the static performance of the tilting-pad gas bearing. Based on the computational results, the influences of the bearing parameters, such as bearing preload, compressible number on the static performance of the bearing are studied.2. Two computational methods for calculating the dynamic stiffness and damping coefficients of the tilting-pad bearings are presented with the assumption that the pads and the journal perturb with the same frequency. Now, the gas-lubricated dynamic Reynolds equation is solved by means of the partial derivative method in the complex number domain. By comparing the results, these two methods are proved to be validity for calculating the dynamic coefficients of the tilting-pad bearings. Moreover, according to the numerical simulation results, the effects of the bearing parameters on the dynamic coefficients are discussed. And the frequency dependency of the dynamic stiffness and damping coefficients of the tilting-pad gas bearings are explained more thoroughly. Furthermore, the each function of the perturbation frequency of the journal and the pads on these dynamic coefficients are firstly discussed.3. By using the limit theory, the limits of the dynamic stiffness and damping coefficients of the tilting-pad bearings are calculated when the dimensionless perturbation frequency tends to zero and infinite. It provides a computational method for predicting the static stiffness and damping coefficients of the tilting-pad bearings and makes it possible to research the dynamic performance of the tilting-pad gas bearings in the whole frequency range.4. Basing on whether the pads tilting degrees of freedom are included in the moving equations or not, two calculation models for the stability analysis of the rotor systems supported by tilting-pad self-acting gas bearings are given. The stability of the rotor systems are analyzed according to the eigenvalues of the system in which the frequency dependency of the dynamic stiffness and damping coefficients are taken into account. It perfects the stability analysis of the rotor systems supported by tilting-pad gas bearings. The results indicate the eigenvalues and the stability of the rotor system obtained by these two models are well agreement each other.5. By using the piezo-electric actuators and PID feedback control systems, an actively control model are firstly established for controlling the vibration of the rotor systems. The optimal control rules between the voltages and displacements of the rotor systems are obtained by means of the optimal control theory. Applying this actively control model, the unbalance responses of the rotor systems can be effectively restrained and the theoretical basis is provided for further improving the stability of the rotor systems supported by the tilting-pad gas bearings.6. A multifunctional test rig is built for testing the static and dynamic performance of the compliant foil journal and thrust bearings. And the testing methods of the static and dynamic performance of the foil bearings are given. The lift-off speed of compliant foil bearing is identified more accurately by simultaneously using the frictional moment method and the displacement response frequency spectra method. The dynamic stiffness and damping coefficients of compliant foil journal bearing are evaluated by means of the least mean square in the time domain. And the effects of the excitation frequency on these dynamic coefficients are mainly investigated. Furthermore, the lift-off speed of compliant foil thrust bearing is first identified by using the displacement response frequency spectra method.更多还原