壓電式無閥門微幫浦在不同彈性及幾何條件下的行為之數值研究

Abstract

本論文將噴嘴/擴散器式的無閥式微幫浦以商業軟體ANSYS旗下的固體及流體數值計算模組進行雙向流固耦合數值模擬，藉由施予幫浦不同的彈性條件及小幅度的改變幾何模型後，觀察固體幫浦結構及流體在不同頻率區間的運動行為特徵，並與實驗流量數值做比較。本研究首先討論了不同耦合條件對微幫浦運動行為的影響，由實驗結果可知，本研究中的微幫浦在不同的交流電頻率作用下會擁有兩個流量區域及兩個不同大小及頻率的流量峰值，而模擬結果顯示只有在進、出口腔體為彈性而非剛性時才會擁有實驗所觀測到的第二流量區現象出現，其流量值遠高於第一流量區，且第一與第二流量區兩者的運動行為也差異甚大。而進、出口腔為剛性的其餘模型皆只有第一流量區。另外與振動片正對的中央振動腔結構為剛性條件時其流量會比彈性條件來的高。之後吾人改變了進、出口腔體的幾何大小，發現若其縮小至一定程度後可視為剛性，其運動行為與無縮小進、出口腔但彈性條件設定為剛性的原模型相同，但流量較大。改變噴嘴與擴散器頸部的流道寬度，模擬結果顯示第一流量區流量減少，而第二流量區的流量增加，但流量峰值頻率幾乎沒有變動。改變整體幫浦結構的壓克力楊氏模數，模擬結果顯示壓克力楊氏模數越大，第一及第二流量區的流量都有顯著的上升，峰值頻率也會往較高頻區域移動。

In this thesis, valveless nozzle / diffuser-based micropumps are simulated by two-way fluid-structure interaction which use of structure and fluid numerical calculation modules of ANSYS which is engineering simulation software. By giving different elastic conditions and changing the geometric model of the pump, we observe the structure of the pump and fluid in different frequency of movement behavior and compare with the experimental data. In this study, we first discuss the effect of different fluid-structure interaction conditions on the micropumps’ motion. The experimental results show that, there are two flow zones and two flow peaks under different AC frequencies in the micropump in the study. From the simulation results, the second flow zone phenomenon observed in the experiment will only appear the models which inlet and outlet chamber’s structure are elastic rather than rigid. This flow rate is much higher than the first flow rate zone. The motions of the pumps models are different between first flow rate zone and second flow rate zone. The other models which inlet and outlet chambers are rigid only have first flow rate zone. In addition, if the structure of middle chamber which is opposite to the vibrating plate is rigid, its flow rate will be higher than the elastic. Then we make the models’ inlet and outlet chambers smaller, so theirs can be regarded as rigid. The motion of the models are the same with the original models which have rigid inlet and outlet chambers, but the flow rate of the models which inlet and outlet chamber are changed are higher than the original. We change the narrowest flow channel width at the nozzle and diffuser. The simulation results showed that the flow rate in the first flow rate zone decreased and the flow rate in the second flow rate zone increased, but the peak flow rate frequency has almost no change. Finally, changing the Young's modulus of acrylic which constitute the pump structure. The simulation results show that if the pump structure have larger Young's modulus, the flow rate of first and second flow rate zone would have a significant increase and the peak frequency would move to higher frequency.