考虑稀薄气体有效黏度的微轴承弹流润滑研究

Elastoaerodynamic Performance Analysis of Gas Microbearings Considering Effective Viscosity in Microfluidic Devices

气体稀薄效应和轴瓦弹性变形对微流体设备中气体微型轴承润滑特性影响显著。根据Veijola提出的稀薄气体有效黏度模型,采用有限元法建立柔度矩阵计算轴瓦表面弹性变形量,并推导考虑有效黏度与弹性变形影响的修正Reynolds方程。通过联立求解超薄气膜润滑修正Reynolds方程、稀薄气体有效黏度方程和三维轴瓦弹性方程,分析轴瓦弹性模量、气体有效黏度、轴承结构参数以及扰动频率对其静动态特性的影响。结果表明:气体稀薄效应显著降低了微型轴承的承载能力;微型轴承的承载力随偏心率和轴承数的增加而增大;增加轴瓦柔性可提高微型轴承的承载能力和摩擦因数,而考虑气体有效黏度的弹性微型轴承承载力和摩擦因数较小;相比刚性表面微气体滑动轴承,轴瓦弹性模量的减小显著增加了动态刚度系数且降低了微型轴承的直接阻尼系数,而考虑稀薄效应引起的气体有效黏度效应降低了轴承直接刚度的同时增加了直接阻尼系数。

Elastic deformation and gaseous rarefaction effects are of great importance to the static and dynamic characteristics of gas microbearings.Based on the effective viscosity model of Veijola, the flexibility matrix was established by finite element method to calculate the elastic deformation of bearing shell surface, and the modified Reynolds equation considering the influence of effective viscosity and elastic deformation was deduced.The effects of bearing elastic modulus, gas effective viscosity, bearing structural parameters and disturbance frequency on the static and dynamic characteristics were analyzed by solving the modified Reynolds equation, effective viscosity equation and elasticity equations of ultra-thin gas film lubrication.The results indicate that the gaseous rarefaction effect significantly reduces the load carrying capacity of microbearings.The load carrying capacity of microbearing increases with the increase of eccentricity ratio and bearing number.Increasing the flexibility of bearing shell can improve the load carrying capacity and friction coefficient of microbearings, while the bearing capacity and friction coefficient of elastic microbearings considering the effective viscosity of gas are small.Compared with the rigid bearing, the reduction of the elastic modulus of the bearing shell significantly increases the dynamic stiffness coefficient and reduces the direct damping coefficient of the microbearings, while considering the gas effective viscosity effect caused by the rarefaction effect reduces the direct stiffness and increases the direct damping coefficient of the microbearings.