| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 95 === This study proposed a new-type self-pumping micromixer which has two valve-less PZT micropumps in parallel arrangement. The rapid mixing was obtained by unsteady mixing mechanism which was due to the periodic variation of the flow at both inlets. This mixing effect is also affected by the oscillating frequency and the phase difference between the two inlet streams. High-quality mixing can be obtained in very short distance so that the device could be reduced to a very small size.
In this study, experiments on the mixing effects were carried out by using two different channel geometries and three phase differences, 0°(in-phase), 90°and 180°(anti-phase). A CCD with illumination by a double-pulsing Nd-YAG laser was used to capture the flow images for the mixing process. Mixing efficiency was thus obtained by evaluating the grey scales of the images. The current results showed that higher mixing quality was obtained when in anti-phase conditions than that in in-phase condition. The results also indicated that the two inlet-streams can not be kept at the same flow rate in phase difference of 90°. For the in-phase conditions, better mixing efficiency was obtained when the larger impinging energy of fluids was generated by higher excitation voltage. For the anti-phase conditions, the existence of crescent-shape interface and the stretch-and-fold phenomenon at the confluence had pronounced effect on the mixing. Better flow mixing can be obtained by using higher driving voltage.
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