噴嘴/擴散器式微幫浦之數值模擬及理論分析

Abstract

本文是以計算流體力學的方法在分析噴嘴/擴散器式微幫浦內的流場與效率。計算時使用非結構性和非交錯式網格；對於速度與壓力的偶合則採取PISO演算法則並以有限體積法將統御方程式離散化。而模擬此流場時是採用不同出口壓力為邊界條件，並計算幫浦之淨流量。 本文針對Ollson【5】的單腔式微幫浦進行分析，主要是探討不同背壓下幫浦的性能。在研究中測試了不同的壓電薄膜的近似曲線對於流量的影響，結果顯示較佳的近似曲線會使得模擬與實驗結果較為穩合，不同近似曲線會影響微幫浦的淨流量。而當增加出口背壓時，流量與效率會隨之減少。此外，本文採用了兩數學種模式來分析噴嘴/擴散器元件，找出了噴嘴/擴散器元件的壓力係數Kn,Kd 與流量的關係，並且將其應用在lumped mass 理論。透過此簡易的理論，便可分析微幫浦不同背壓下的流量、效率及腔體中心壓力、。本研究中比較了模擬和理論的結果，發現此理論估算的結果與模擬稍有差異，為了解決此問題，本文發展出了不同的方式估算效率，以使得此理論在效率的估算的準確性提高，而具有較高的可用度

In this thesis, CFD is used to analyze viscous flow and efficiency of micropumps . Unstructured and nonstaggered meshes are adopted in computations.The PISO algorithm is used to take the velocity-pressure coupling and the governing equations are discretized by the finite volume method. Pressure boundary condition was apply in our simulation.In this thesis, a single chamber Micropump pump [5] is analyzed and we explore the pumping performance. The PZT is approximated by different mathematical curves.Testing indicates that the approximated curve need to be optimized to achieve better results. Different approximated curves will affect the pumping flow. When the back pressure is increased，the flow rate and pump efficiency get lower.In order to find the pressure coefficient Kn&Kd of the Nozzle/Diffuser, we analysis the Nozzle/Diffuser element by using two different models.Furthermore,we use the lumped mass model to analyze the net flow and umping efficiency of the micorpump in different back pressures.We compare the results of the 3D simulation and the lumped model.It was shown that there exits a little difference certain degree of difference between the two models.To solve this problem，we develop a different method to calculated the pump efficiency. This method improve the accuracy of the theorical solution and make Lumped Mass Model more useful .