涡轮分子泵入口结构改进的计算研究

Novel Caliber Adaptor for Matching of Turbo Molecular Pump Inlet and Container Outlet: A Simulation Study

针对涡轮分子泵的入口管道束流效应和涡轮端盖反射效应对传输几率的不利影响、以及大口径涡轮分子泵与小型仪器相连接的难题,本文提出分子泵入口结构的改进方案:将涡轮转子的平板端盖改成锥形反射屏结构,把过渡连接件做成圆弧过渡段结构。文中根据实际结构参数,建立了不同结构类型的计算模型,采用试验粒子蒙特卡洛方法,基于自由分子流态基本假设,利用Molflow+软件,计算了各个结构模型的传输几率。计算结果表明:当倾角α的取值范围在60°～70°、圆锥底角β的取值范围在25°～45°之间时,理论上可将涡轮分子泵的抽气速率提升5%左右。

A novel type of caliber adaptor was developed to match large inlet-diameter of turbo molecular pump and small outlet-diameter of vacuum container. The caliber adapter comprises a conical reflective screen over the flat turbine,a truncated cone with curved wall and large/small diameter flanges. The flow field in the caliber adaptor was mathematically modeled,theoretically analyzed with free molecular flow assumption and in test particle Monte Carlo method,and numerically simulated with Molflow + software. The influence of the adaptor geometry on the transmission probability was investigated for design optimization. The simulated results show that the dip-angle( α)of the truncated cone and the base-angle( β) of the conical reflective screen have a major impact. To be specific,the new caliber adaptor,with α in 60° ~ 70°and β in 25° ~ 45° ranges,theoretically increases the pumping rate of turbo molecular pump by about 5%.