Experiment and numerical simulation of a valveless piezoelectric micropump applying Coanda effect

摘要

To improve the flowrate and the volumetric efficiency of the valveless piezoelectric micropump, a valveless piezoelectric micropump based on Coanda effect was designed and fabricated by Polymethylmethacrylate (PMMA). Its performance including the flowrate and the maximum back pressure, optimum operating condition, working principle as well as the diffuser angle were discussed. An experiment was carried out to obtain the performance of the micropump and search for the optimum operating condition. The high-speed photograph was utilized to obtain the instantaneous volume changing rate of the chamber in the experiment. A numerical simulation was done to obtain the flow field of the micropump to specialize its working principle. To discuss the effects of the diffuser angle on the performance, the flowrate and the volumetric efficiency of the micropumps with different diffuser angles from 30 degrees to 45 degrees were studied by the numerical simulation. The numerical simulation results were compared with the experimental data. The findings reveal that the micropump with the diffuser angle of 45 degrees can achieve the flowrate of 5.4 ml.min(-1) and the maximum back pressure of 2.82 kPa in the optimum operating condition, 300 Vp-p for the driving voltage and 25 Hz for the frequency. The suitable range of the diffuser angle is about from 30 degrees to 45 degrees. When the maximum Reynolds number is over 600, the entrained flowrate caused by Coanda effect can contribute a over 50% volumetric efficiency to the micropump.