無閥式微幫浦之腔體設計與作動機制研究

A Study on Chamber Design and Flow Mechanism of Valveless Micropump

謝明哲(Ming-Che Hsieh)

指導教授 ： 王安邦

國立臺灣大學/工學院/應用力學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00062

摘要

本研究透過專利與期刊論文之檢索首先針對機械薄膜微幫浦的各式動力源與閥門結構作一趨勢分析，結果發現「壓電式」動力源為所有研究應用之主流；微幫浦可依閥門分為「有閥」與「無閥」兩大類；有閥又可分為主動閥與被動閥，而被動閥在歷年專利與論文的累積數量上皆占第一，但其近幾年之成長已趨向飽和，故可知此一技術發展已邁入成熟期。目前業界側重於微幫浦的主動閥研究，而在學界因為無閥式結構簡單、不需耗能且無疲勞、阻塞等特色，在近幾年大幅成長漸成主流，但其也意味著無閥式微幫浦仍在萌芽開發期，甚具高發展性與可專利性，因此，吾人選定壓電無閥式微幫浦為本文之主題。
有別於傳統利用微機電技術所製作之矽晶片微幫浦，吾人採用塑膠基材與雷射加工之方式以節省模型製程開發的時間與成本。另外，因為目前無閥式微幫浦的研究皆僅止於整流器之創新設計，尚未有文獻針對振動腔內之流場作分析，所以本文在流體力學相似律的基礎上，藉由流場可視化與流力分析，在文獻中第一次系統性探討微幫浦設計參數對振動腔內渦漩發展型態之影響。由流場分析結果發現：振動腔內最大渦漩之尺寸，決定於進、出口渦漩流之發展及其與腔體壁的相互作用。而本文也發現：微幫浦之流體傳輸效率與進、出口渦漩對之發展緊密相關；例如：平均流場之出口端渦漩對的「中心距」、「中心眼位置」、「出口端平均噴流速度」以及「渦漩對平均強度」，皆與幫浦效率之消長有完全一致之趨勢。而後，吾人更進一步依據上述流場渦漩發展之分析，並參考澎湖七美「雙心石滬」之幾何構形，設計出一全新的無閥式雙心振動腔體之微幫浦設計，實驗結果發現幫浦效率可明顯提升約一倍。
此外，本文也對噴嘴/擴散器的效能探討，發現改變擴散器之張角(2θ)、細長比(L1/W1) 及喉部入口設計等之效能趨勢皆與習知巨觀水力試驗裡的擴散器結果一致。在本文之實驗雷諾數範圍(Re=50~100)下，吾人發現擴散器的最佳設計為2θ=10o及L1/W1=18。而吾人亦改變噴嘴/擴散器的相對位置(定義為旋轉角α)，發現在α為45度與135度時，流量各約有30%、15%之提升；但在α為90度時性能卻沒有改變。而在多進(口)、多出(口)之微幫浦設計測試中，可發現兩進一出之設計約有20%流量之增加；但在一進兩出之設計淨流量則明顯縮減約40%。上述結果說明改變噴嘴/擴散器之相對位置與進、出口數量會對腔體內漩之發展情況造成影響，而使得幫浦的效率有所變異。
另外，微流元件性能之重複性在過往的相關文獻鮮少被提及，經常可發現其容易受環境因素或製程的影響使得性能難以被維持或重現。因此吾人在本文也發展出一標準實驗加工及測試流程，以確保本文各項設計參數實驗結果之可信度及可重複性。
本文最後利用力與電流類比的方式建立一無閥式微幫浦經驗模型，可提供作為變更設計參數時，估算系統共振頻之參考輔助工具。

關鍵字

壓電無閥式微幫浦 ； 渦漩對 ； 擴張角 ； 旋轉角 ； 多流道進出口 ； 雙心型振動腔設計 ； 內流場可視化 ； 微幫浦經驗模型

並列摘要

The research analyzed the trend of various kinds of “actuators” and “valves” of mechanical membrane micropump by patent and jounal paper searching. “Piezoelectirc” actuator is the most popular one in all researches and applications. The valve of micropump can be divided into “with valve” and “no valve (valveless)” two types, and the fore is classified into “active” and “passive” types. Athough the passive valve is with the greatest numbers of papers and patents, it has gradually been in the mature period. Nowadays, the industry puts emphasis on the active valve research of micropump, but the valveless research is gradually popular with the academic because of its merits of “no fatigue”, “easy fabrication.” This means “valveless micropump” is in the developing period and with high possibility of patenting. Therefore, “piezoeletirc valveless micropump” is choosen as my researching topic.
The research used plastic materials to fabricate the valveless micropump in order to dispense with fabrication time and capital. And the effect of designed parameters on the patterns of two vortex pairs in the pumping chamber were systematically discussed by the flow visualization system.
By the establishment of flow visualization system, “the core distance”, “the core position of vortex pair”, “jet mean velocity”, and “mean vortices” at the outlet diffuser are highly related to the pumping efficiency in the quasi-steady flow. Further, a novel design of vibrating chamber which was based on the concept of “double-hearted stone tidal weirs” in the Penghu island and the experimental analysis of vortex development inside the chamber was proposed. The new design can elevate the rectification efficiency, and be applied in various kinds of micro-valve designs for each kinds of mechanical membrane pump.
The diffuser opening angle (2θ), aspect ratio (L1/W1) and the inlet design at the throat were varied to find that the pumping efficiency which has the same trend as diffusers in the macroscopic hydraulic experiment. The results showed that the optimal design of nozzle/diffuser is diffuser angle 10o and aspect ratio 18. Besides, there is a reverse direction flow happening due to the asymmetric 3D recirculation flow at the diffuser wall with a larger opening angle 70o. When varying the relative position of inlet and outlet diffuser or numbers of inlet and outlet, it would change the vortex patterns inside the chamber and also the pumping efficiency.
The repeatability of microfluidic element performance is hardly mentioned in the past literatures. The performace is hard to be maintained because of some environmental and manufacturing problems. Consequently, a standard machining and testing process are developed to confirm the credibility and repeatability of experimental results.
In the last part of the paper, the method of ”force-current analogy” is utlized to empirically model the micropump in order to provide the guidelines of preliminary pump design and instantly estimate the resonant frequency and flow trend.

並列關鍵字

PZT valveless micropump ； vortex pair ； diffuser angle ； rotating angle ； multi inlets and outlets ； double-hearted vibrating chamber design ； flow visualization ； micropump analogy empirical modeling

參考文獻

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