微尺度下空气静压支撑在滑移区的承载特性实验研究

Experimental Study on Bearing Characteristics of Air Static Pressure Support at Micro Scale in Slip Region

为了阐释空气静压导轨气膜间隙处在微小尺度所体现的特性,引入努森数(Kn),计算了不同工况下气膜内压力和不同气膜厚度下Kn数的变化关系。引入支撑区气膜分层假设,与分子动力学相结合,对气膜内不同流态层的刚度进行了实验和分析。通过ANSYS仿真和实验数据相结合得出了结论:气膜内稀薄效应的增强,可以一定程度上提高气浮支撑的静承载能力。气浮支撑的刚度特性和气膜内部分层情况有关:以分子碰撞运动为主的稀薄层主要起容性效应,实现分子间动量的传递和转化,因此该层所体现出来的刚度较差;以惯性力驱动的连续流层内部分子运动比较稳定,特别是在垂直方向不存在显著的动能和压力能之间的转化,因此该层的刚度特性较强。实验证明,气膜厚度在1~10μm时,气膜的刚度先增大后减小,也间接论证了静压支撑的刚度特性主要由气膜内连续流层决定。

In order to explain air hydrostatic guideway gas film clearance characteristics embodied in micro scale, we introduce the Knudsen number, and calculate the gas film pressure under different conditions and under different film thickness Knudsen number changes. The assumption of gas film stratification in the support zone is intro- duced, and combined with the molecular dynamics, the rigidity of the different fluid layers in the gas film is experimented and analyzed. Through the combination of ANSYS simulation and experimental data, the conclusion is drawn that the enhancement of the thin gas film can improve the static bearing capacity of the air bearing. The air bearing stiffness characteristics of the gas film internal stratification is connected with： the thin layer of molecular collision motion mainly plays the capacitive effect, which can transfer and transform the intermolecular momentum, so the rigidity of this layer is poor; the internal molecular motion of the continuous flow layer driven by inertial force is relatively stable, especially there is no significant kinetic energy and pressure energy in the vertical direction be- tween the transformation, so the stiffness of the layer is strong. The Experiments show that along with the gas film thickness changes from 1 microns to 10 microns, the gas film stiffness increases first and then decreases, but also indirectly demonstrate the stiffness characteristics of air block is mainly composed of gas film continuous layer.