稀薄效应对空气静压导轨速度边界和温度特性的影响

EFFECTS OF RAREFIED GAS FLOW ON VELOCITY BOUNDARY AND TEMPERATURE CHARACTERISTICS OF AEROSTATIC GUIDE WAY

当空气静压导轨气膜厚度为微米级别时,依据Kn数定义可知此时气膜内流动可能处于滑移区,气浮支撑的内部压力和承载特性会受到稀薄效应的影响,最典型的表现为边界速度滑移和温度跃迁现象。将基于格子Boltzmann方法研究稀薄效应对空气静压导轨速度边界和温度特性的影响,得到气膜径向速度和温度分布。通过机理分析和数值计算发现:随着Kn数的增大,速度滑移程度增大;而速度滑移间接引起黏温效应,导致边界温度跳跃现象。温度跳跃相当于在导轨与气膜之间的一个附加热阻,增加流动的摩擦损耗,影响散热。

When the thickness of aerostatic guide way gas film is in the scale of micron meters,the air flow inside is in the slip regime according to Kn. In this case,pressure distribution and bearing characteristics of the gas film will be influenced by rarefied effect. The most outstanding characteristics is shown as velocity slip and temperature jump. Based on LBM,velocity and temperature distribution in the radial direction can be achieved. Based on the study of a mathematical model and simulation analysis,with the increase of Kn,the degree of velocity slip increases. The result of velocity slip benefit cooling effectiveness,but the temperature jump is negative. This is because temperature jump acts as an additional thermal resistance between rail and air film,which is not beneficial to radiating of aerostatic guide way.