A Study of Micro-Two Phase Flow Generator

本研究已初步的發展出一新型的微二相流濃度梯度產生器；此濃度梯度產生器藉由微二相流的產生、分離與結合，成功的產生出具有濃度差異的微液滴。 壓克力微加工為本實驗用於晶片製作的製程方法，有別於微機電製程，其好處為降低製作成本，且大大的縮短利用微機電製程所花費的時間；因近年來實驗室晶片(lab on a chip)的蓬勃發展，與晶片需具備有高的整合性，故本研究考慮到微二相流產生晶片其下游若需與其他晶片整合時，其因另一晶片所造成的阻抗改變是否會影響到微二相流產生的尺寸？然而在針對微二相流產生的文獻中，並無這方面的相關研究，故本研究在微二相流產生部份針對流道出口背壓變化的影響進行討論；且針對不同的流道比例α(定義為：連續相流道寬度/不連續相流道寬度比)，亦進行探討，發現在本實驗所給予最大背壓6.8kpa條件下，無論α為何，都不影響微二相流的產生尺寸；另外也發現，出口背壓的控制，可使微二相流的產生有很好的重複性，吾人亦與文獻比對，本文數據明顯優於文獻上所得的結果。而關於α參數的影響：α越大，液滴的尺寸會越小。而無論在任何α條件下，液滴的尺寸會隨著連續相黏度的增加而變小。另外文獻上一個無實驗驗證的假設：不連續相的黏度並不影響液滴的產生，本文的實驗結果顯示：不連續相的黏度的增加在不同的α條件下，對於微二相流的尺寸確無明顯的變化，但會影響微二相流產生的型態圖(flow map)，意即隨著不連續相的黏度增加，其產生段塞流(slug flow)的區域會隨之變小，故並不盡如文獻上的假設可將不連續相黏度的影響忽略。 另外對於液滴二次分離部份，吾人考慮到晶片使用的簡單性，選擇被動式的液滴二次分離進行研究；並以調控其下游的流阻，以簡易的控制二出口背壓調控液滴二次分離的比例，液滴的最大分離比例可優於文獻上的值達到10.8倍。In this study, a new type- Micro-two phase flow concentration gradient generator has been demonstrated. This generator generated droplets with different concentration by Micro-two phase flow generation, separation and combination. Plastic micro-machining is the method to fabricate the chip in this study. The advantages of this method are reducing fabrication cost and saving time. Due to high integration of chip, it is considered that the Micro-two phase flow chip needs to integrate with the other chips. And the resistance from the other chips wether influences the size of droplet generation must be considered. Since, there are no related researches in literatures. This study discusses the effect of integration resistance by changing the back pressure. To different α(Definition is: Continuous phase channel width/dispersed phase channel) were also discussed. The result showed that the outle pressure did not affect the size of droplet different choice of α. Compare to lteratures, it was found that the outlet pressure control would effective improve the uniformity of droplet size in my own research. For effect of α, the droplet size will decrease as increasing of α. In the continuous phase, for different choice of α, the smaller the droplet size is, the lager the viscosity is. Most of them assumed that the viscosity of dispersed phase flow does not affect the size of droplet in the literatures. However, the result in my own research showed that the viscosity of dispersed phase does not affect the size of droplet. But, the droplet generation type (flow map) has obvious influence. With increasing viscosity of dispersed phase flow, the area of slug flow will decrease. So, the viscosity of dispersed phase flow can not be neglected in the research of droplet formation. In addition to separation of droplet, there were many methods of droplet separation including active and passive noes. Considering the simplification of chip, the passive method was chosen in this study. The downstream resistance in passive separation method has an extreme influence on separation ratio. Since the control of downstream rsistance from the past literatures can not satisfy the condition in my study, the simple method which is using back pressure controller to adjust the ratio of droplet separation. And, comparing to the maximum ratio of droplet separation 7.5, my study has already successfully made ratio achive 10.8