A Study on Chamber Design and Flow Mechanism of Valveless Micropump
Date Issued
2009
Date
2009
Author(s)
Hsieh, Ming-Che
Abstract
The research analyzed the trend of various kinds of “actuators” and “valves” of mechanical membrane micropump by patent and jounal paper searching. “Piezoelectirc” actuator is the most popular one in all researches and applications. The valve of micropump can be divided into “with valve” and “no valve (valveless)” two types, and the fore is classified into “active” and “passive” types. Athough the passive valve is with the greatest numbers of papers and patents, it has gradually been in the mature period. Nowadays, the industry puts emphasis on the active valve research of micropump, but the valveless research is gradually popular with the academic because of its merits of “no fatigue”, “easy fabrication.” This means “valveless micropump” is in the developing period and with high possibility of patenting. Therefore, “piezoeletirc valveless micropump” is choosen as my researching topic. The research used plastic materials to fabricate the valveless micropump in order to dispense with fabrication time and capital. And the effect of designed parameters on the patterns of two vortex pairs in the pumping chamber were systematically discussed by the flow visualization system. By the establishment of flow visualization system, “the core distance”, “the core position of vortex pair”, “jet mean velocity”, and “mean vortices” at the outlet diffuser are highly related to the pumping efficiency in the quasi-steady flow. Further, a novel design of vibrating chamber which was based on the concept of “double-hearted stone tidal weirs” in the Penghu island and the experimental analysis of vortex development inside the chamber was proposed. The new design can elevate the rectification efficiency, and be applied in various kinds of micro-valve designs for each kinds of mechanical membrane pump. The diffuser opening angle (2θ), aspect ratio (L1/W1) and the inlet design at the throat were varied to find that the pumping efficiency which has the same trend as diffusers in the macroscopic hydraulic experiment. The results showed that the optimal design of nozzle/diffuser is diffuser angle 10o and aspect ratio 18. Besides, there is a reverse direction flow happening due to the asymmetric 3D recirculation flow at the diffuser wall with a larger opening angle 70o. When varying the relative position of inlet and outlet diffuser or numbers of inlet and outlet, it would change the vortex patterns inside the chamber and also the pumping efficiency. The repeatability of microfluidic element performance is hardly mentioned in the past literatures. The performace is hard to be maintained because of some environmental and manufacturing problems. Consequently, a standard machining and testing process are developed to confirm the credibility and repeatability of experimental results. In the last part of the paper, the method of ”force-current analogy” is utlized to empirically model the micropump in order to provide the guidelines of preliminary pump design and instantly estimate the resonant frequency and flow trend.
Subjects
PZT valveless micropump
vortex pair
diffuser angle
rotating angle
multi inlets and outlets
double-hearted vibrating chamber design
flow visualization
micropump analogy empirical modeling
Type
thesis
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