魯式幫浦之熱流特性模擬

Abstract

魯式真空幫浦廣泛使用在各式各樣的真空幫浦應用系統上，然而，對於影響魯式幫浦的效率或對於設計幫浦有極重要影響的幫浦內部流場變化情形，卻很少有論文研究。本研究的主要目的在於研究魯式幫浦內部整體的流場、溫度場及壓力場的變化，並且模擬經由轉子與轉子或轉子與腔體壁面之間間隙洩漏的情形。 以往這方面的研究，基於數值計算上的限制，大多數只能做到靜態模擬，無法實際模擬出暫態流體流經魯式真空幫浦的真實狀態；本文的計算方法是運用數值計算軟體Star-CD來模擬魯式幫浦運轉時的暫態分析。結果得知，魯式幫浦腔體內部會產生激烈的溫度及壓力變化；並且雖然魯式幫浦是連續抽取氣體，但是會隨轉子轉動呈現週期震盪變化，間隙間的洩漏亦會隨著轉子轉動而有不同的洩漏量。

Roots vacuum pump is widely used in vacuum pumping systems. Based upon the operating mechanism of the Roots vacuum pump, the variations of pressure, temperature, mass flow rate, etc. in the Roots vacuum pump are at transient state, which causes the analysis to be extremely complicated. Then, all the studies investigating gas properties in the Roots vacuum pump were under steady state. The aim of the study is to utilize a CFD code of “Star-CD” and to investigate the gas properties during the Roots vacuum pump operated. Two situation are taken into consideration, one is the Roots vacuum pump set in the middle of a pipe of which both sides are open, and another one is a closed container vacuumed by the Roots vacuum pump. From the results of the simulation, it can be found that there are drastic variations in temperature and pressure, and the variations are periodic with rotating angle, The mass flow rate discharge from the decreases gradually, and the pressure wave moves forward and backward alternatively in the pipe.