应用有限体积法空气静压导轨力学特性的研究

空气静压润滑是精密工程领域的关键技术之一，润滑气膜的压强分布、承载能力、刚度等力学特性是决定导轨稳定性的主要因素。目前，空气静压导轨设计中常采用简化雷诺方程的工程计算方法，存在静态性能误差大的特点。本文针对润滑气膜的压强分布规律、承载力等主要力学特性参数进行研究。基于节流孔出射气流为冲击射流，引入计算流体力学的有限体积法，应用理想气体等温条件下的k-ε模型封闭控制方程组对润滑气膜的力学特性进行数值分析，得出不同气膜厚度下空气静压导轨工作面上的压强分布规律。数值结果表明：导轨内气膜从节流孔沿工作面到导轨边缘的压强分布规律非雷诺润滑方程所给出的均匀递减变化，而是在节流孔附近存在半径约为500µm的负压区、峰值约为0.05MPa；在静压导轨气膜厚度与承载力分析的基础上，指出气膜与导轨间的气固耦合所引发的导轨弹性自激振动是空气静压导轨实现纳米级定位的主要制约因素。

Study on mechanical characteristics of aerostatic bearing with finite volume method

Aerostatic lubricating is the key technology in the field of precision engineering. The mechanical characteristics of air film, such as pressure distributing, bearing capacity and stiffness is the main factor that determine the stability of air-bearing position. Simplified Reynolds equation is widely employed in aerostatic bearing design, which leads large static error. This paper does research work on mechanical characteristics of aerostatic bearing such as pressure distributing principle, bearing capacity. Going on the premise that jetting air from orifice has the attribute of air impingement jet, the paper introduces finite volume method of computational fluid dynamics (CFD), applies control equation set k-ε model closed of isothermal air for mechanical characteristics numerical analysis of air film and unveils the pressure distributing principle of different thickness air film on aerostatic bearing working plane. The numerical analysis shows that the pressure distributing principle of air film from orifice to edge of air-bearing along the working plane is not degression mentioned by simplified Reynolds equation, but fluctuation that the air flow pressure sharply drops under the atmospheric pressure nearby orifices, then gradually increases above the atmospheric pressure and reverses finally. Based on the analysis of air film thickness and aerostatic -bearing bearing capacity, this paper points out that elastic self-excited vibration caused by gas-solid coupled between air film and aerostatic bearing is the main block of aerostatic bearing’s application in nano-positioning.