【作者】 吴超；

【导师】 陈晓阳； 王文；

【作者基本信息】 上海大学 ， 机械设计及理论， 2008， 博士

【摘要】 油膜轴承是转子-轴承系统的关键支承部件,对转子系统的稳定运行起着非常重要的作用。随着转子系统向着高速、高精度和高负荷的方向发展,对油膜轴承性能的要求越来越高,而尝试对传统油膜轴承进行改进以提高其性能一直是从事该领域研究人员的追求目标之一。本文提出了一种新型的具有主动控制功能的油膜轴承,该轴承利用超磁致伸缩微位移驱动器(GMA)对油膜轴承位置进行静态调节,并能动态主动抑制转子-轴承系统的振动,达到提高油膜轴承定位精度和稳定性的目的。论文以带有GMA的新型主动控制油膜轴承为研究对象,完成的主要工作有:参考已有的应用在位置定位和声纳激励等方面的GMA设计,考虑油膜轴承的应用特点,设计了结构上更为简单的专用GMA。建立了该GMA的静态位移力模型和动态机-磁耦合模型,搭建了杠杆试验装置,验证了GMA在常态磁场强度下可以产生与油膜轴承油膜厚度在同一数量级的伸长量。在材料试验机上做了GMA在各种频率下的动态性能试验,验证了GMA在输入电流频率达到800Hz时有好的频响特性,能满足遏止转子-轴承系统振动所需的频率。研究了GMA在止推轴承中的应用,验证了GMA在油膜轴承实际工况下调整油膜间隙的能力,同时解决了一些结构的止推轴承中因瓦块间的不均载导致的局部瓦温过高的情况。编制了相关程序,分析了止推轴承的油膜间隙与瓦块的最大温升和承载量的敏感性关系,表明通过控制瓦块支承处的油膜间隙可以有效地改变单瓦块的承载量并调节单瓦块温升。搭建了以GMA来主动调节瓦块油膜间隙的止推轴承实验台,该轴承以瓦块的温度作为反馈信号,控制支承瓦块的GMA的伸长量,改变止推瓦块的油膜间隙,使各个瓦块承受的载荷均匀,防止局部瓦块的过高的温升。在止推油膜轴承实验台上,进行了均载调节试验,验证了GMA调节瓦温的能力。建立了可控径向油膜轴承支承的Jeffcott转子系统模型,进行了动力学分析。纳入GMA的机-磁耦合模型,采用龙格-库塔法编制了考虑基础参振的径向油膜轴承-转子系统的计算程序。该程序根据非线性油膜力数据库技术计算油膜力,以轴颈的振动信号作为反馈信号来同步控制轴承座的运动,计算得到了轴心运动轨迹,并详细考察了控制增益和相位差对系统不平衡振动和稳定性的影响。计算结果表明,控制增益和相位差对系统不平衡振动影响很大,选择合适的控制增益和相位差可以大大减小系统的不平衡工频振动,减小系统的半频涡动,大大提高系统的稳定性。计算结果还说明,对于某一固定的控制增益,存在一个最佳相位差,能使系统的不平衡响应最小。搭建了可控径向油膜轴承-转子系统实验台和测控系统。作为初步验证可控油膜轴承性能的实验台,转子支承一端采用可控滑动轴承,另一端采用向心滚动轴承的简单结构;为了满足轴承在不同转速下的试验需要,以变频器和电主轴系统作为驱动装置。根据GMA的驱动特点,采用碟形弹簧结构给GMA施加预应力,能保证滑动轴承套和GMA始终不脱离,同时满足滑动轴承套具有两个自由度的要求。进行不同载荷和转速下的可控滑动轴承的调心试验,通过改变GMA的磁场,可以把不同工况下的可控滑动轴承支承的转子的轴心的静平衡位置调整到同一位置,验证可控滑动轴承具有良好的定心精度。针对工频振动,进行了动态轴心轨迹控制试验。初步试验结果表明可控滑动轴承所支承的转子的工频振动幅值大大减少,轴心动态振动轨迹明显减小,验证了本文提出的具有主动控制功能的油膜轴承具有较好的振动抑制能力,使传统油膜轴承的的稳定性得到提高。更多还原

【Abstract】 As the key supporting components for rotor-bearing system, hydrodynamic oil film bearing have much important effect on the stability of rotor-bearing system. With development of rotor-bearing system capacity, high speed, high precision and heavy loading, better performance oil film bearing are needed to meet present rotational equipment requirement. It is a hot research area to improve fluid film bearing performance. In this thesis, a new active controllable oil film bearing is put forward in order to improve the bearing performance. By making use of the giant magnetostrictive actuators (GMA), the location of oil film bearing can be actively controlled and vibration of the rotor-bearing system can also be restrained dynamically. This doctoral project is mainly on the investigation of this newly developed bearing with GMA and the main works have been done are as follows:Based on the design of present GMA used in the position allocation and sonar excitation, etc., the special GMA for oil film bearing is designed. Its structure is simpler. Working condition, needed excitation and amplitude adjustment range for oil film bearing are also considered in the design of this GMA. Besides, static displacement-force model and dynamic mechanical-magnetic coupling model for GMA are established. A simple lever rig is built up to measure static extension of GMA. The static tests have been done under different magnetic field and pre-loading force. The test results are consistent with the GMA static displacement-force model. It is also measured in the test that the GMA can extend several tens of micrometers, which is at the same order of the clearance of oil film bearing. Dynamic tests of GMA have also been done under different excitation frequency of current using the material test rig. The special GMA has good dynamic response when exciting current frequency attains 800Hz, which can almost meet the requirement of restraining vibration of rotor-bearing system with oil film bearing. These primary researches show that the designed GMA is fit to control oil film clearance and also have potential to restrain vibration of rotational machine supported with oil film bearing.Application of GMA in thrust bearing is investigated in order to verify the capacity of GMA to adjust oil film clearance and solve the problem that some pads in thrust bearing have excessive temperature due to inhomogeneous loads on pads. A numerical calculation program is developed to analyze the sensitive relationship among oil film clearance, the maximum temperature and the load on a pad. The results indicate that the load on a pad can be changed and temperature rise can be adjusted by controlling oil film clearance at the supporting place of the pad. Based on this, an active controllable hydrodynamic thrust bearing is put forward by using GMA to adjust oil film clearance. A thrust bearing test rig has been built up and experiments were done to verify the performance of the thrust bearing.The dynamics of Jeffcott rotor system model supported by active controllable journal bearing is analyzed. A numerical calculation program for journal bearing-rotor system is developed considering the mechanical-magnetic coupling model of GMA and excitation from the bearing. The nonlinear oil film force database is used to calculate oil-film forces of hydrodynamic journal bearing in this program. The shaft vibration signal is taken as the feedback signal to control the excitation current on GMA. Runge-kutta integral method is adopted to calculate the journal center loci. Calculated results show that phase difference and control gain have important effect on unbalance vibration and stability of the system. It also shows that appropriate phase difference and control gain can greatly reduce unbalance vibration and whirl vibration. It can improve the stability of the system. Results also imply that there is an optimal phase difference value which can minimize the unbalance vibration for a certain control gain.The developed controllable journal bearing rig with GMA is built up. Its test control system is given. As a preliminary rig to verify the controllable journal bearing performance, one end of the rotor is supported by a controllable hydrodynamic bearing and the other end by a radial ball bearing. Besides, electricity spindle and converter are used to drive the rotor-bearing test rig to meet the test requirement at different speed. Washer spring is used to add GMA with preloading according to the driven requirement of GMA. It also can assure that hydrodynamic bearing sleeve is always contacted with GMA and has two moving degree of freedom.The auto-centering tests of the controllable bearing are done and results are firstly presented. The shaft center can be adjusted to the same position under different loads and speeds by changing GMA’s magnetic field. The results show that controllable hydrodynamic bearing has good auto-centering function.Tests on the vibration compression function of the bearing also have been done and introduced. The test results indicate that the unbalance vibration can be restrained obviously. These tests imply that controllable journal hydrodynamic bearing with GMA has very good potential to improve the stability and rotational accuracy of rotor-bearing system.更多还原