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The Research on Flow Characteristics of High Vacuum Valve

Author: QiWeiHong
Tutor: BaoGang
School: Harbin Institute of Technology
Course: Mechanical and Electronic Engineering
Keywords: high vacuum valve flow characteristics air flow molecular flow conductance
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Type: Master's thesis
Year: 2012
Downloads: 10
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Abstract


The application region of vacuum system in heavy industry and light industry ismore and more wide, and the requirements on performance of vacuum systembecome more high. So there is a need to study deeply about the flow characteristicsof vacuum components, especially that of high vacuum valve. Nevertheless, therehave been little researches on flow characteristics of vacuum components withcomplex structure, and many relative theories have not been perfected. Therefore,the conductance of high vacuum valve is required to be obtained through relevantstudy. As a result, the valve can work best in the vacuum system.This paper takes high vacuum valves used in vacuum system as research object.First of all, the conductance value of simplified model of high vacuum valve,right-angle elbow pipe, is calculated both in air flow and molecular flow conditionaccording to existing theoretical formula. In air flow condition, the simulationmodel is established using FLUENT software on the basis of computational fluiddynamics. The conductance information varying with pressure is acquired andconductance curve for a same valve with different opening of valve core. Inmolecular flow regime, the transmission probability and conductance curve of highvacuum valve with different opening of valve core is calculated using MATLABsoftware based on Test Particle Monte Carlo Method, and the calculated resultsmeet well with the reference value. In transitional flow regime, the conductance isreceived by exponential fitting of conductance value got in air flow and molecularflow regime. Thus conductance curve of high vacuum valve in the whole pressurerange can be obtained.Due to restrictions in terms of experimental equipment, it is difficult to validatesimulation results through real experiment. Therefore this paper would compare thesimulation results with existing experimental results of flow characteristics for thesame model. Then the correctness of calculated results of high vacuum valve can bedemonstrated indirectly.Besides, the inner structure of high vacuum valve becomes more and morecomplicated, and to calculate conductance according to theoretical formula is notconvenient either not accurate. But the conductance value got by simulation canmore precisely reflect the flow characteristics of high vacuum valve in practicalworking conditions as well as would provide certain theoretical basis for the design, manufacture and application of high vacuum valve or other vacuum componentswith complex structure.

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