气固热耦合对微尺度气膜空气静压轴承承载特性的影响

Effect of Gas-solid Thermal Coupling on Loading Capacity of Aerostatic Bearing Under Micro-scale Gas-film

当空气静压轴承工作气膜处在微米尺度时,气膜内压力分布具有显著的温度敏感性,严重影响轴承系统的承载能力和刚度特性.本文基于气体润滑理论和稀薄气体动力学,结合边界滑移和热耦合分析技术,通过数值分析的方法研究考虑温度影响所引起的空气静压轴承气膜局部变形问题,对系统的承载能力和刚度特性进行理论分析和实验研究.研究结果表明:气固热耦合效应会使微米级气膜内部发生不均匀的膨胀变形,导致空气静压轴承内部流场发生变化.气膜的最大变形量随温度升高呈线性增长,当温度达到250℃后趋于稳定;随着气膜厚度的增加,空气静压轴承气膜内部对温度的敏感性逐渐减小;考虑热耦合效应的轴承压力分布和承载能力低于传统层流假设下理论计算所得结果,因而在高精密、微米级气膜和极端温度条件等场合设计使用空气静压轴承时,必须要考虑环境温度和系统工作温升带来的热耦合效应影响.

When the aer0static bearing working gas film is at the micron-scale,the pressure distribution in the gas film has a significant temperature sensitivity,which seriously affects the loading capacity and stiffness characteristics of the bearings system. Based on the theory of gas lubrication and rarefied gas dynamics,combined with boundary slip and thermal coupling analysis,this paper studies the local deformation of aerostatic bearing caused by temperature influence by numerical analysis method,and theoretically analyses and experimentally studies the loading capacity and stiffness characteristics of the system. The results show that the gas-solid thermal coupling effect will cause uneven swelling deformation in the micron-scale gas film,resulting in the change of the internal flow field of the aerostatic bearing. The maximum deformation of the gas film increases linearly with the temperature rise,and is stabilized when the temperature reaches 250 ℃. With the increase of the gas film thickness,the sensitivity of the gas film inside the aerostatic bearing to the temperature decreases gradually. Considering the thermal coupling effect,the bearing pressure distribution and loading capacity are lower than the conventional laminar flow hypothesis,therefore,in the high-precision,micron-level gas film and extreme temperature conditions such as the design of the use of aerostatic bearings,it is necessary to take into account the environmental temperature and the temperature rise of the system to bring about the effect of thermal coupling effect.