- 學位論文
流體特性對圓管內長氣泡發展影響之研究
The Effect of Fluid Properties on the Evolution of a Long Bubble in a Circular Tube
摘要
本研究在探討長氣泡在圓管中穿透矽油和揮發性溶劑之行為，在此實驗裡，質量流量控制器是用來控制氣體注入量，藉由不同氣體注入量來觀測比較氣泡形狀之演化。 本研究方法是藉由高速照相機擷取氣泡成長之影像，氣泡平均速度是藉氣泡位移量除以兩張照片時間差來求得。而氣泡直徑經影像處理方法求出，液體之殘留率及氣泡之中空率便可藉由氣泡直徑算出，至於毛細係數及雷諾數則藉由氣泡速度值來算出。 實驗結果顯示，當氣體流量固定時，隨矽油黏度增加，氣泡速度變得更快。當矽油黏度固定，氣體流量越高時，毛細係數和雷諾數跟著變大，但中空率卻變小。在充滿揮發性溶劑直管中，直管中因氣泡移動速度之改變，會產生某種暫態現象，此暫態形狀定義為蘑菇氣泡。當揮發性溶劑揮發速率≧1時，氣泡移動之雷諾數達到某ㄧ區間時便會產生蘑菇氣泡。當揮發性溶劑揮發速率＜1，不管氣泡移動之Re值如何改變，皆不會產生蘑菇氣泡。丙酮、甲醇和乙酸丁酯之雷諾數分別在4381~4430、2460~2490和1940~1980時皆會產生蘑菇氣泡。
並列摘要
This study investigated the properties of long bubbles penetrating silicone oil and volatile organic compounds (VOCs) in a circular tube. In this experiment, the volume rate of the injection of gas was controlled by using a mass flow controller (MFC). The profile and the evolution of the bubble were observed and compared for various volume flow rates of the injection gas. The evolution images of bubbles were captured by a high-speed camera in this study. The average velocity of the bubble was obtained from the bubble displacement divided by the time difference between two frames. The diameters of bubbles were obtained from the image processing method. The fractional converge (m) of the liquid and the hollow ratio (λ) of the bubbles were estimated by the diameters of bubbles. The Capillary number (Ca) and Reynolds number (Re) were calculated by the velocity of bubbles. The experimental results showed that the bubble velocity got faster as the silicone oil viscosity increases under a constant gas flow. For silicone oil with constant viscosity, as the gas flow rate got higher, then Ca and Re were also larger; however, λ was smaller. As the VOCs filled in circular tube, the velocity of bubble had changed, a specific transient response occurred. The transient shape was defined mushroom bubbles. As the evaporation rate of VOCs ≧1, mushroom bubbles were expected to occur as the Reynolds number (Re) reached a certain region. As the VOCs evaporation rate ＜1, the mushroom bubble phenomenon did not occur, regardless how the Re values had changed. When the Re values for acetone, methyl alcohol and butyl acetate were between 4381~4430, 2460~2490 and 1940~1980, respectively, the transient response phenomenon occurred.