蓄能机组轴系振动及推力轴承三维热弹流耦合特性研究

发布时间：2018-02-22 19:24

本文关键词： 蓄能机组转子动力学推力轴承热弹流润滑流固热耦合　出处：《清华大学》2016年博士论文　论文类型：学位论文

【摘要】：在水力、机械、电磁等多种复杂因素的影响下,尤其是在工况转换过程中,抽水蓄能机组的轴系振动问题非常突出。推力轴承作为承受轴向载荷的核心部件,在频繁的开停机过程中容易发生磨损故障,直接影响机组的安全稳定运行。推力轴承润滑特性本质上是典型的流、固、热三场耦合问题。开展水、机、电三方面因素对蓄能机组轴系动力学特性的影响分析以及推力轴承热弹流润滑特性研究具有重要意义。本研究主要展开了以下三方面的工作:应用转子动力学有限元法深入研究了机架系统、发电机不平衡磁拉力、滑动轴承刚度系数对蓄能机组轴系模态特性的影响,并进行了水轮机稳态工况和开机、停机过渡过程工况的轴系动力响应分析。建立了综合考虑不平衡磁拉力和包含机架系统的轴系动力学分析模型,能够更加准确地描述蓄能机组轴系机械-电磁耦合关系。此外,发现了转轮内部不对称流动引起的间隙内部压力不均是转轮水力不平衡力的主要来源。计算得到的稳态工况和过渡过程工况轴系摆度和轴向振动的结果与实测基本吻合,提供了一种新的分析轴系响应的方法。应用流、固、热耦合的方法深入研究了蓄能机组双向可倾瓦推力轴承热弹流润滑特性。通过引入附加人工阻尼来迟滞瓦块和推力头的运动速度,保证了油膜厚度在迭代过程中的收敛性。分析了轴承瓦块自适应倾斜机理及油膜热量耗散特性,获得了油膜热油转移因子和瓦块自由表面对流换热系数。重点探讨了瓦块支撑径向和周向偏心率对润滑性能的影响。研究了蓄能机组在水轮机工况和水泵工况开停机过程中的瞬态热弹流特性。分析了高压油顶起状态轴承静压润滑特性,探讨了变速过程中油膜压力、温度、厚度等特性的变化规律,发现了瓦面倾斜角相对转速的滞后性,以及升速过程中瓦面的快速温升导致瓦面产生显著的瞬态热变形,而降速过程中瓦面的快速温降则有助于减小瓦面的瞬态热变形。本文的研究揭示了推力轴承瞬态热弹流润滑机理,为蓄能机组推力轴承的优化设计和安全运行提供了有力的技术指导。
[Abstract]:Under the influence of many complicated factors, such as hydraulic, mechanical, electromagnetic and so on, especially in the process of changing working conditions, the vibration problem of shaft system of pumped storage unit is very prominent. In the course of frequent opening and downtime, it is easy to occur wear and tear failure, which directly affects the safe and stable operation of the unit. The lubrication characteristics of thrust bearings are essentially a typical coupling problem of flow, solid and heat fields. The influence of three aspects of electricity on the dynamic characteristics of shafting of storage units and the study of thermo-elastohydrodynamic lubrication of thrust bearings are of great significance. The main work of this study is as follows: the application of rotor dynamics. The finite element method is used to study the frame system. The influence of the unbalanced magnetic pull force and the stiffness coefficient of sliding bearing on the modal characteristics of the shafting of the storage unit are carried out, and the steady condition and start-up of the turbine are carried out. The dynamic response of shafting under transient condition of shutdown is analyzed. A dynamic analysis model of shafting with unbalanced magnetic tension and frame system is established, which can more accurately describe the mechanical-electromagnetic coupling relationship of shafting of storage units. It is found that the uneven pressure in the gap caused by asymmetric flow in the runner is the main source of the hydraulic unbalance force of the runner. The calculated results of shafting pendulum and axial vibration under steady and transient conditions are in good agreement with the measured results. A new method for analyzing shafting response is provided. The thermo-elastohydrodynamic lubrication characteristics of the bidirectional tilting pad thrust bearing of a storage unit are studied by means of thermal coupling. The velocity of the tile and thrust head is retarded by the introduction of additional artificial damping. The convergence of the oil film thickness in the iterative process is ensured. The adaptive tilting mechanism of the bearing tile and the heat dissipation characteristics of the oil film are analyzed. The oil film heat oil transfer factor and convection heat transfer coefficient of tile free surface are obtained. The influence of radial and circumferential eccentricity of tile support on lubrication performance is discussed. Transient thermoelastohydrodynamic characteristics during shutdown. The hydrostatic lubrication characteristics of bearings with high pressure oil jacking state are analyzed. The variation law of oil film pressure, temperature, thickness and other characteristics in the process of changing speed is discussed. It is found that the lag property of the relative rotational speed of the tilting angle of the tile surface and the remarkable transient thermal deformation of the tile surface caused by the rapid temperature rise of the tile surface in the process of raising the speed. However, the rapid temperature drop of the bearing surface is helpful to reduce the transient thermal deformation of the bearing surface during the deceleration process. In this paper, the mechanism of transient thermo-elastohydrodynamic lubrication of thrust bearing is revealed. It provides powerful technical guidance for optimization design and safe operation of thrust bearing of storage unit.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TV743;TV734

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