真空系统抽气过程的计算方法研究

有关抽真空系统的计算方法一般采用简单的理论模型,其结果与实际情况有较大偏差.该文以中低真空系统(包括真空室、管道和真空泵)为研究对象,基于真空泵的抽气速率与吸入压力的特性关系,根据管路流动状态选取层流或湍流模型,提出一种新的抽真空时间计算方法.选取某实测的真空系统作为案例,采用新计算方法和传统的层流算法对该系统抽真空过程分别进行了计算,发现在中高压阶段,管道流动处于湍流状态并使阻力增大,若不考虑湍流影响,则所得到的压力下降过快与实际情况有较大偏差.该文所提出的计算方法得到了实测结果的验证,从而是一种切实可行的抽真空时间计算方法.

The Study on the Calculation Method for Pumping Process in a Vacuum System

The calculation methods for vacuum pumping system are usually based on some simple theoretical models,so the corresponding results have significant deviations from the actual situations.In this study,the medium and low vacuum systems(including vacuum chambers,pipes and vacuum pumps)are taken as research objects.Based on the characteristic relationship between vacuum pump's suction flowrate and inlet pressure,a novel calculation method for vacuum pumping time,in which either the laminar model or the turbulent model is selected according to the flow state of the pipeline,is proposed.A measured vacuum system is taken as example for calculation.The proposed method and traditional laminar method are respectively used to calculate the vacuum process of this system.It is found that in the middle and high pressure stage the pipeline flow is in a turbulent state and the resistance is increased.If the influence of turbulence is ignored,the calculated pressure drop will be faster and greatly deviated from actual situation.The calculation method proposed in this study was verified by actual measurement results,indicating that the method is practical for vacuum pumping time calculation.