壓電式無閥門壓克力微幫浦振動腔在不同彈性模數及不同支撐下的行為研究

Abstract

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數值模擬分析，在建立包覆振動腔的彈性體模型後，透過調整彈性體的固定條件和楊氏模數探討其對微幫浦性能的影響，並和實驗的流量比較，找出最貼近實驗結果的模擬方法。 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，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且可信。 由數值計算結果可以發現，在改變支撐條件的部分，當包覆振動腔的彈性體拘束越大時，共振頻偏高，反之拘束越小則共振頻偏低。主導流量的是彈性底部，當底部為彈性時流量會大幅下降。另外由於建立的彈性體模型在振動腔側壁和實驗上並不完全吻合，本文也探討了彈性體側壁設定的拘束條件對於微幫浦的影響，結果為側壁的設定條件對於模擬結果的改變僅在於高低頻能量衰減速度上。 另外在改變楊氏模數的部分，楊氏模數越低則流量越低，共振頻也越向左移，在對比壓電片頂部和底部彈性體的位移後發現兩者之間的運動有存在相位差，腔體內壓力和出口流出速度亦不完全相對。 最後透過適當的邊界條件和楊氏模數找到最貼近實驗數據的模擬數值，並透過振動腔內壓力和流速的變化討論其在一個週期內運動的狀態。本文附有模擬之設定方式。

This paper used the ANSYS software to perform numerical analysis on the efficiency for the valveless nozzle/diffuser-based micropump. By designing the elastic chamber, and changing the elastic constants of chamber to the micropump in order to discuss its influence on the pumping efficiency. This paper not only compared the flow rate between simulations and experiments, but also discussed and analyzed the simulation fluid field with experimental results, in order to know more details of the fluid mechanism. Unlike the common method in the simulation of micropump, the simulating model in this paper is established to be more complete by considering piezoelectric materials, the structure of micropump, and the flow field in all. Conventionally, CFD software processes fluid-structure interaction using moving boundary method. Instead, this paper used ANSYS and ANSYS CFX for the structural and fluid domains, respectively. Both the structural and fluid domains are coupled in the three-dimensional simulation. The simulation results are closer to reality than the moving boundary. From the numerical results under changing the boundary conditions, the moreconstraints the chamber is imposed, the higher resonant frequency it is. The flow rate would be much more smaller when the base is elastic. When changing the elastic constant of bottom cover of the chamber, the lower elastic constants are, the smaller flow rate would be, and the resonant frequency shifts to the left. We get the numerical results which agree well with the experimental data by taking an appropriate boundary conditions and elastic constants. In addition, we also discuss the motion of chamber in one period through the pressure and velocity change inside the chamber.