- 學位論文
真空系統抽氣曲線之模擬與軟體開發
Pump-Down Curve Simulation and Software Development for Vacuum Systems
摘要
本論文提出一方法來模擬真空腔體內壓力對於時間之抽氣曲線，所用之理論包括氣體定律、對於不同氣流狀態之氣導、管件之等效長度、釋氣、擴散與滲透等。為了能有效率地分析，本論文也開發出一模擬程式，其由MFC與MATLAB組成。MFC用來輸入必要之參數，其包括欲預估壓力範圍之起始壓力與目標壓力、腔體之體積與內表面積、抽氣管路之配置、真空幫浦之性能與氣體負荷，MATLAB則利用相關理論來計算抽氣曲線。描述真空腔體內質量平衡之統御方程式是由Temkin等溫線推導出。在計算完管件之等效長度並藉由雷諾數與紐森數將預估壓力範圍分為數段後，每段之抽氣曲線計算可分為三個步驟，其依序為計算管件之氣導、真空幫浦之有效抽氣速率與抽氣時間。本論文所模擬之抽氣曲線與兩不同真空系統之實驗進行比較，除此之外，其也與商業軟體VacTran之模擬結果相較。由相較結果得知，本論文所提出之模擬程式可確地預估從低真空度至高真空度之抽氣曲線。
並列摘要
This paper presents a method to simulate pressure versus time pump down curve for vacuum chambers. Related basic theories, including gas laws, conductance for several kinds of flow regimes, equivalent length for pipes, outgassing, diffusion, and permeation etc., are used to simulate the pump-down curve. The simulation program consists of a MFC module and a MATLAB module. The MFC module is used to input necessary parameters, including start and target pressure for desired simulation pressure range, volume and inner surface area of vacuum chambers, configuration of pumping lines, performance of vacuum pumps, and gas loads. The MATLAB module deals with the pump-down curve calculation based on related theories. The governing equation of the conservation of mass in a pumped vacuum chamber is derived from extended Temkin isotherm. After equivalent length for pipes are calculated and the simulation pressure range is separated into several segments by Knudsen’s number and Reynolds’ number, the pump-down curve of each segment is simulated by three steps, including calculating the conductance of pipes for corresponding gas flow regimes, the effective pumping speed of vacuum pumps and finally pump-down time. The simulated results are compared with the experiment of two different vacuum systems and the results simulated by the commercial software, VacTran. The developed program can simulate the pump-down curve with good accuracy in the range from low vacuum pressure to high vacuum pressure.