考虑激振频率的可倾瓦推力轴承动特性理论与试验研究

Theoretical and Experimental Study on the Dynamic Characteristics of Tilting Pad Thrust Bearing Considering Excitation Frequency

为了研究激振频率对可倾瓦推力轴承动特性的影响,提出考虑激振频率的动特性建模方法和试验方法。依据可倾瓦轴承刚度和阻尼定义,将激振频率引入可倾瓦推力轴承动特性计算过程,通过建立轴向扰动下的膜厚方程、雷诺方程及瓦块运动方程,推导出包含激振频率的可倾瓦推力轴承动特性数学模型,计算分析刚度和阻尼随扰动频率(激振频率与主轴转频的比值)、转速及载荷的变化规律;采用脉冲激振法在可倾瓦推力轴承试验台进行动特性试验,得到不同激振频率、转速及载荷条件下刚度、阻尼的试验结果,并和相应的理论计算值进行对比分析。结果表明:当扰动频率较小时,可倾瓦推力轴承刚度随其增加而逐步增大,阻尼随其增加而逐步减小;当扰动频率增加到一定程度后,其刚度和阻尼逐步趋于稳定。此外,转速和载荷对其刚度和阻尼随扰动频率的变化幅度基本无影响。

A modeling and testing method of dynamic characteristics considering excitation frequency of tilting pad trust bearing are proposed to study the effect of the excitation frequency on its dynamic characteristics. The excitation frequency is introduced into calculation process of dynamic coefficients of tilting pad thrust bearing according to the definition of stiffness and damping of tilting pad bearings. The mathematical model of its dynamic characteristics containing excitation frequency is deduced through establishing fluid film thickness equation, Reynolds equation and equation of tile motion under the condition of axial disturbance. The variation of stiffness and damping with perturbation frequency, that is, the ratio of excitation frequency to spindle rotation frequency, speed and load are analyzed. Test results of stiffness and damping in different excitation frequency, rotation speeds and loads are obtained in the test rig of tilting pad trust bearing by using impulse excitation method. The following conclusions are obtained through analyzing the theoretical and test results. When the perturbation frequency is small, the stiffness of tilting pad thrust bearing increases gradually with its enlargement, the damping is just the opposite. While the stiffness and damping tend to be stable gradually after perturbation frequency increases to a certain degree. In addition, the amplitude of variation of stiffness and damping with perturbation frequency is little affected by speed and load.