弹性箔片动压气体止推轴承-转子系统动力学特性研究

发布时间：2018-01-19 14:01

本文关键词： 动压气体止推轴承轴向承载力润滑膜厚度静动特性弯曲刚度轴向及弯曲振动　出处：《哈尔滨工业大学》2012年硕士论文　论文类型：学位论文

【摘要】：弹性箔片动压气体轴承是以柔性表面为支承的自作用式动压挠性轴承，具有质量小、可靠性高、维修周期长、环境与温度适应性强、功率损失小等诸多优点，主要包括径向和止推箔片轴承两种结构形式20世纪六七十年代以来，随着航空航天、原子能、低温工程等技术的发展，弹性箔片动压气体径向轴承逐渐应用到无油透平、低温膨胀机以及飞机的空气循环机等高速旋转机械中。与径向轴承相比，弹性箔片动压气体止推轴承的发展相对缓慢，对其动压气膜的机理研究也不够深入。鉴于此，本文以波箔型动压气体止推轴承为基础，理论分析其静、动态特性，并对止推轴承—转子系统的动力学特性进行研究。首先，建立柱坐标下适合动压气体止推轴承的压力控制Reynolds方程，，选用合适的箔片变形模型，采用Newton-Raphson迭代法和有限差分法相结合，耦合求解Reynolds方程和润滑膜厚度方程。利用上述方法研究转子止推盘未倾斜和倾斜状态下，弹性箔片动压气体止推轴承的静态特性。与相同参数刚性表面止推轴承的结果对比分析表明：弹性箔片动压气体止推轴承可获得与刚性表面止推轴承相当的轴向承载力，同时其粘性摩擦力矩较小，所需驱动力也小。通过分析结构参数、间隙参数以及转速等因素对止推轴承静态特性的影响规律，为弹性箔片动压气体止推轴承的静态性能优化提供理论依据。基于小扰动法建立止推轴承润滑膜压力微分量与轴向位移及速度的关系表达式，采用有限差分法进行求解，获得止推轴承的动力学特性系数。分析转子止推盘倾斜状态下润滑膜压力分布特点，计算止推轴承的弯曲刚度。对比刚性表面和弹性箔片动压气体止推轴承动力学特性系数结果可知，弹性箔片动压气体止推轴承的动力学特性系数小于刚性表面止推轴承的结果。最后进行参数研究，优化弹性箔片动压气体止推轴承的动态性能。根据动态特性分析结果，选择合适的止推轴承动力学特性系数，建立止推轴承—转子系统有限元模型，计算转子轴向、弯曲振动临界转速以及不平衡响应。结果表明，转子轴向振动临界转速较大，但一阶临界转速通常在极限转速之下，工作时应避开该临界转速一定范围。另一方面，弹性箔片动压气体止推轴承可起到加强径向轴承刚度的作用。
[Abstract]:Flexible foil hydrodynamic gas bearing is a self-acting dynamic flexible bearing supported by flexible surface. It has many advantages such as small quality, high reliability, long maintenance period, strong adaptability to environment and temperature, small power loss and so on. Mainly includes radial and thrust foil bearing structure form since 20th century, with the development of aerospace, atomic energy, cryogenic engineering and other technologies. Elastic foil hydrodynamic gas radial bearings are gradually applied to high-speed rotating machinery such as oil-free turbine, low temperature expander and aircraft air circulation machine. The development of elastic foil dynamic gas thrust bearing is relatively slow, and the mechanism of dynamic pressure gas film is not deep enough. In view of this, this paper based on the wave foil dynamic pressure gas thrust bearing, theoretical analysis of its static. Dynamic characteristics and dynamic characteristics of thrust bearing-rotor system are studied. Firstly, the pressure control Reynolds equation suitable for hydrodynamic gas thrust bearing is established in cylindrical coordinates, and the appropriate foil deformation model is selected. The Newton-Raphson iterative method and the finite difference method are used. The Reynolds equation and the lubrication film thickness equation are solved by coupling. Static characteristics of elastic foil hydrodynamic thrust bearing. The results of comparison with rigid surface thrust bearing with the same parameters show that:. The axial bearing capacity of the elastic foil hydrodynamic thrust bearing is equivalent to that of the rigid surface thrust bearing. At the same time, the viscous friction torque is small and the driving force is small. By analyzing the influence of structural parameters, clearance parameters and rotational speed on the static characteristics of thrust bearing. It provides the theoretical basis for the static performance optimization of the dynamic pressure gas thrust bearing with elastic foil. Based on the small perturbation method, the relationship between the differential pressure of lubricating film and axial displacement and velocity of thrust bearing is established, and the finite difference method is used to solve the problem. The dynamic characteristic coefficient of thrust bearing is obtained, and the pressure distribution of lubricating film is analyzed under the condition of rotor thrust disc tilting. The bending stiffness of thrust bearing is calculated. Compared with the dynamic characteristic coefficient results of rigid surface and elastic foil hydrodynamic thrust bearing. The dynamic characteristic coefficient of the gas thrust bearing with elastic foil is smaller than that of the thrust bearing with rigid surface. Finally, the parameters are studied to optimize the dynamic performance of the gas thrust bearing with elastic foil. According to the results of dynamic characteristic analysis, the finite element model of thrust bearing-rotor system is established and the rotor axial direction is calculated by selecting the appropriate dynamic characteristic coefficient of thrust bearing. The results show that the critical speed of axial vibration of rotor is large, but the first order critical speed is usually below the limit speed. On the other hand, the elastic foil hydrodynamic thrust bearing can strengthen the stiffness of radial bearing.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH133.3

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