Simulation And Analysis Of Valveless Piezoelectric Micropump Based On Coanda Effect Based On Multiphysics Coupling

As the key component of the microfluidic system,the valveless piezoelectric micropump has the advantages of small volume,low consumption of energy and timeliness of response.So,it has always played an important role in the fields of aerospace,biomedical and electronic cooling systems.At present,the research on piezoelectric micropumps is mostly limited to a single domain,and there are few studies on the coupling between multiple physical fields in the pump.Therefore,to analyze the output performance and flow field characteristics of the micropump under multi-field coupling,in this paper,the valveless piezoelectric micropump based on Coanda effect is taken as the research object,and numerical analysis and experiments were used to study the micropump.The main research contents are as follows:Firstly,an experimental platform was built.The output performance of the valveless piezoelectric micropump based on Coanda effect and the diffusion/nozzle valveless piezoelectric micropump in the excitation voltage range of 70 to 250V_ppp and the excitation frequency range of 25 to 100 Hz has been studied through experiments.The experiment results show that when the frequency is 50 Hz,the flow rate of the two micropumps increases with the increase of voltage;when the voltage is 200V_pp,the flow rate of the two micropumps increases first and then decreases with the increase of frequency.The two pumps achieved maximum flow rates at 62.5 Hz and87.5 Hz,respectively,0.703 ml/min and 0.423 ml/min.When the voltage is 200V_pp,the flow rate of the micropump and the outlet pressure change with frequency are the same.Within the excitation range studied in this paper,the valveless piezoelectric micropump based on Coanda effect has better output performance than the diffusion/nozzle valveless piezoelectric micropump.In addition,the output performance of the valveless piezoelectric micropump based on Coanda effect under three different excitation waveform loading has also been studied.The results show that the output performance of the micropump driven by the sine wave is better than the micropump driven by the triangular wave,and the micropump driven by the square wave is relatively impressive in the output flow,but it is accompanied by a harsh buzzing sound during the test Therefore,the sine wave is the most suitable driving waveform for the valveless piezoelectric micropump based on Coanda effect.Secondly,using multi-field coupling numerical simulation,in this paper,the performance of the piezoelectric vibrator under multi-field coupling was studied.The results of numerical simulation show that the first-order mode is the mode with the largest volume change of the piezoelectric vibrator;the effect of multi-field coupling only changes the maximum amplitude of the vibrator and does not change the distribution of the displacement of the piezoelectric vibrator.Affected by the coupling,the output flow of the piezoelectric pump and the maximum amplitude of the piezoelectric vibrator lag the excitation voltage,and the lag time increases as the frequency increases.During the pumping process of the micropump,the maximum stress appears at the edge of the elastic substrate;During the suction process of the micropump,the maximum stress occurs at the edge of the elastic substrate and its junction with the piezoelectric diaphragm.Thirdly,using multi-field coupling numerical simulation,in this paper,the effects of excitation parameters?excitation waveform,excitation frequency f?and structural parameters?Aspect Ratio of throat H/d,diffusion angle??on the performance of the micropump were studied.The results show that the sine wave is the most suitable excitation waveform for the micropump;when the voltage is 200V_pp,the optimal frequency of the micropump appears at 62.5Hz;when the voltage is 200V_ppp and the frequency is 50 Hz,the diffusion angle?is 30°to 60°,H/d is in the range of 0.5 to2.5,the flow rate of the micropump increases with the increase of the diffusion angle,first increases and then decreases as the aspect ratio increases,and at?=60°,H/d=2,the flow rate of the micropump reaches the maximum.Analysis of the amplitude curve of the piezoelectric vibrator and the velocity vector diagram of the flow field in the pump found that the output flow of the micropump is determined by the maximum amplitude of the piezoelectric vibrator and the position and scale of the vortex formed in the pump during the pumping process.