稀薄条件下平板间润滑气膜内速度滑移现象分析

发布时间：2019-03-21 18:34

【摘要】：空气静压导轨润滑气膜工作在微米级时,内部气流受稀薄效应影响,沿流动方向压力和流速的变化规律与宏观计算所得差异较大。在气膜高度方向上,由于特征尺度减小,气体分子间作用效果加剧,传统忽略垂直方向压力梯度变化的假设不再成立,气膜内部不仅呈现较明显的分层趋势,并且速度滑移现象越发显著。通过LAMMPS(大规模原子分子并行模拟器)、LBM(离散格子玻尔兹曼方法)和Fluent等方法模拟气膜支撑区气体流态并计算其流速和压力,得出了相关结论:润滑气膜内沿气体流动方向分为压力驱动区和牛顿摩擦区,沿高度方向分为近壁层、稀薄层、连续流层,速度滑移主要发生在压力驱动区的近壁层和稀薄层。气膜分层及速度滑移现象存在于压力驱动区和牛顿摩擦区;压力驱动区的气膜分层及速度滑移随气体流速的增加而增强,牛顿摩擦区的气膜分层逐渐弱化,速度滑移现象逐渐退化为近壁面边界层。
[Abstract]:When the lubrication film of the aerostatic guide is in the micron level, the internal air flow is affected by the rarefaction effect, and the variation law of the pressure and velocity along the flow direction is quite different from that obtained by the macroscopical calculation. In the gas film height direction, due to the decrease of the characteristic scale and the aggravation of the interaction between the gas molecules, the assumption that the pressure gradient in the vertical direction is ignored is no longer valid, and the gas film is not only showing a obvious trend of stratification in the inner part of the film. And the phenomenon of velocity slip is more and more obvious. In this paper, LAMMPS (large scale atomic and molecular parallel simulator), LBM (discrete lattice Boltzmann method) and Fluent are used to simulate the gas flow state and calculate the velocity and pressure of the gas in the gas film support region. It is concluded that the lubrication gas film is divided into pressure-driven zone and Newtonian friction zone along the direction of gas flow, and along the height direction is divided into near-wall layer, thin layer, continuous layer, velocity slip mainly occurs in the near-wall layer and thin layer of pressure-driven zone. The gas film delamination and velocity slip exist in the pressure-driven region and Newtonian friction region. The gas film delamination and velocity slip in the pressure-driven region increase with the increase of the gas velocity. The gas film stratification in the Newtonian friction region gradually weakens and the velocity slip phenomenon gradually degrades to the boundary layer near the wall.
【作者单位】：昆明理工大学机电工程学院;
【基金】：国家自然科学基金项目(51305185)资助~~
【分类号】：TH136

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