進出口設計對無閥式微幫浦效能影響之數值模擬

Numerical Simulation on the design of Inlet and Outlet in the Valveless Micropump

林家祥(Chia-Hsiang Lin)

指導教授 ： 張正憲

國立臺灣大學/工學院/應用力學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.00773

摘要

本文利用商業軟體ANSYS作為數值模擬的工具，對噴嘴/擴散器式的壓電無閥式微幫浦作流量分析，藉由改變進出口的幾何尺寸，以及緩衝腔體的串聯，探討流阻變化對微幫浦性能的影響。除了比對實驗的流量之外，同時將模擬計算出的流場與實驗上的流場顯影作比較與討論，以對微幫浦內流場變化對於流量的影響有更清楚的瞭解。
與一般常用的模擬微幫浦之方法不同，本文的模型沒有經過簡化，而是考慮壓電材料與微幫浦之間的電、流、固多重耦合分析。本文處理流固耦合所使用的模擬計算方法也有別於一般CFD軟體的移動邊界(moving boundary)，而是透過ANSYS與ANSYS CFX將結構場與流場結合的同步雙向耦合，比起一般的移動邊界法，本文所得到的流場更為擬真。
由數值計算結果可以發現，將進出口尺寸(R)增大為振動腔半徑(Rch)的1.2倍，流量會大幅提升。儘管模擬的流量數值誤差稍大，流量變化的趨勢仍然和實驗大致相符。另外，模擬結果也可看出在微幫浦振動腔前後加入緩衝腔體對流量的提升亦有明顯的改善，尤其在振動腔體前後各置一緩衝腔體的效果最好，此趨勢亦和實驗結果相符。
在實驗上發現當進出口渦漩對和腔體之出口端渦漩對最大時，幫浦的效率最好，而模擬的流場發展趨勢也和實驗結果大致相符。由模擬和實驗的結果，可以證實不管是改變進出口尺寸或是增加緩衝腔體，都能夠減小流阻與提供微幫浦腔體內之渦漩對有更好的發展空間，以提升微幫浦的性能。

關鍵字

壓電無閥式微幫浦 ； 流固耦合數值模擬 ； 進出口尺寸 ； 緩衝腔體

並列摘要

This paper use the ANSYS software to do numerical analysis of flow rate for the valveless nozzle/diffuser-based micropump. By varying the geometrical design of the inlet and outlet, and serially connecting one to several buffer chambers to the micropump in order to discuss its influence on the flow resistance and the pumping efficiency. Besides flow rate, by comparing the simulation flow field with experimental results in order to have more detailed explanation of the flow mechanism.
Unlike the commonly used method of simulated micropump, the pumping performances of a piezoelectric valveless micropump are investivated in terms of the three-dimensional electro-fluid-structural interaction. General CFD software processing fluid-structure interaction using moving boundary method. However, this paper using two-way direct FSI. ANSYS and ANSYS CFX are used for the structural and fluid domains, respectively. Both the structural and fluid domains are coupled in the three-dimensional simulation. The flow field calculated by synchronous two-way coupling is closer to reality than the moving boundary.
The numerical results showed that the flow rate increased substantially when radius for the inlet and outlet was 1.2 times of the chamber. Despite the numerical results are not accurate enough, the trends of simulation roughly match the experimental results. In addition, numerical results also showed the design of buffers can really enhance the performance of micropump, especially the design of each buffer serially connecting on the both sides of the chamber is optimal. These simulations are also consistent with the experimental results.
The flow visualization analysis shows that the best pumping efficiency happened as the vortex pairs of inlet and outlet region and the vortex pair in the vibrating chamber near the outlet diffuser reached maximum. The flow field of simulation also presents similar trends. Consequently, “varying the size of inlet and outlet” and “buffers serially connecting to a vibrating chamber” both could decrease the flow resistance and provided enough space to make the vortex inside chamber develop well. Hence, the micropump performance is obviously enhanced.

並列關鍵字

PZT valveless micropump ； FSI numerical simulation ； size of inlet and outlet ； buffers

參考文獻

16. 謝明哲, "無閥式微幫浦之腔體設計與作動機制研究," 國立台灣大學應用力學研究所碩士論文, 2009.

17. 蔡文惠, "進出口設計對無閥式微幫浦效能影響之實驗探討," 國立台灣大學應用力學研究所碩士論文, 2010.

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