基于速度滑移的气膜流态建模与CFX仿真分析

Analysis of CFX Simulation and Modeling of Flow Pattern of Gas Film Based on Velocity Slip

为了研究空气静压导轨微小间隙中的气膜流态,以提高数控机床的加工精度,通过将速度滑移计算方法及边界条件引入Navier-Stokes方程,推导出适合可压缩气体在微尺度条件下的雷诺方程;利用流体仿真软件CFX对微尺度下湍流状态的气膜流态进行仿真分析;通过改变节流孔直径和气膜厚度分析气膜内压强分布的变化。结果表明,当节流孔直径和气膜厚度在一定范围内变化时,压强由最大值趋于环境压强过程中呈现波动变化趋势;当节流孔直径过大时,气膜内压强不稳定,容易产生气膜波动现象,对机床的加工精度造成影响;当气膜厚度过大时,气膜内压强会出现突变,对气膜支撑力的稳定性影响很大。

In order to research the flow pattern of gas film in micro the machining precision of Numerical Control （NC） machine tool, clearance of an aerostatic guide way, so as to improve through introducing velocity slip calculation method and boundary condition into Navier-Stokes equations, the Reynolds equation suitable for compressible gas in the micro scale condition was deduced. The flow pattern of gas film with turbulence in micro-scale was analyzed using the liquid simulation software CFX. The internal pressure distribution of the gas film was analyzed by changing the orifice diameter and gas film thickness. The results show,when the orifice diameter and gas film thickness change in a certain range, the film pressure has a fluctuation change when it decreases from a maximum to the environmental pressure;when the orifice diameter is too large, the internal pressure of film is not stable, and film fluctuation is appeared easily, which influences the machining precision of machine tool;when gas film thickness is too large, the internal pressure catastrophe appears, it causes larger influence to the stability of the support force of gas film.