摘 要
本研究旨在設計及製作微擴流器在非穩態流場下之損失係數測試平台，流體之驅動係使用陶瓷壓電致動器與活塞結合，並利用都卜勒雷射干涉儀來量測活塞的位移，繼而得到精確的瞬間流量。同時以精密的動態壓力感測器，來量測擴流器兩側之壓力變化。本研究針對擴張角分別為 及 之微擴流器進行動態量測，量測結果可發現，兩種角度的擴流器，其逆向(噴嘴)方向的損失係數大於正向(擴流器)方向的損失係數，而且不論是正向或逆向流場， 擴流器之損失係數都大於 擴流器之損失係數。此外，實驗結果顯示，擴流器最佳的效率與操作頻率有關，擴張角 時，最佳效率發生於頻率為5Hz，擴張角為 時，則為12Hz。

Abstract
The purpose of the present study is to design and fabricate the test platform used for measuring the loss coefficients of microdiffusers under an unsteady flow field. The fluid is pumped by a piston which is driven by a ceramic piezoelectric actuator. The displacement of the piston is measured by a Doppler laser interferometer so that the instantaneous volume flow rate can be obtained. Pressure variations across the microdiffusers are measured by a dynamic pressure sensor. Two microdiffusers with expanding angle of and respectively are tested. Experiment results, show that the loss coefficient in the negative (nozzle) direction is greater than that in the positive (diffuser) direction for both of the microduffusers. Furthermore, for both of the flow directions, the loss coefficient of -diffuser is greater than that of -diffuser. It is also found that the best efficiency of the diffuser depends on operational frequency. The best frequency is 5Hz as the expanding angle is and 12Hz as the expanding angle is .

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