Study On Transient Flow In Piezoelectric Micropump Based On Synthetic Jet

With the advent of the information age,integration and miniaturization has become the development trend in many areas.As the key drive component in microfluidic systems,piezoelectric micropump is now of concern.However,there are some serious shortcomings of the traditional piezoelectric pump.The piezoelectric micropump with valve structure limits its application to a great extent for the existence of the valve structure itself.The traditional noozle/diffuser valveless piezoelectric pump can not flow out continuously and the flow rate is low.This study focuses on the transient flow in piezoelectric micropump based on synthetic jet which is simple and easy to miniaturize and has the advantages of high flow rate and low pulsation continuous output.In order to do the thorough research to this kind of micropump,the following research work is mainly carried out:1)The micro-electromechanical system,microfluidic system and its technology are introduced.The micropump is the key driving components in the microfluidic system whose advantages and disadvantages and the working principle are introduced.The conclusion is that the performance of the valveless pump based on synthetic jet is better,but it lacks of research now,especially with the media water..2)A new type of piezoelectric valveless micropump based on synthetic jet for conveying liquid is proposed,and its working principle is introduced.The driving principle of the piezoelectric oscillator and several models to describe its displacement are summarized.The ANSYS Mechanical module was used to simulate the selected piezoelectric oscillator.The results show that the center point has the biggest displacement and decreases along the radial direction,which can be described as a parabola.The larger the excitation voltage is,the larger the displacement of the piezoelectric oscillator is.3)The numerical simulation method is used to simulate the operation of micropump.The reliability of the turbulence model used in simulation is first confirmed,and then the appropriate numerical simulation settings is selected.Thesimulation results show that the operation of the micropump is consistent with the theory.Under the appropriate excitation condition,the flow can be continuously discharged,and the internal flow field conforms to the characteristics of the synthetic jet.The effects of nozzle length,synthetic jet cavity length,outlet width and frequency on the external characteristics of micropump were investigated.The results show that the length of the nozzle has little effect on the performance of the micropump.When the length of the synthetic jet chamber is the same and Re is 1000,the outlet width is set to 15 Da to reach the largest flow rate,and when the Reynolds number is large(1500,2000),it decreases first and then increases.The flow rates of micropumps increase with the decrease of frequency when the Re is 500,and he trend is just the opposite when Re is1000,1500,2000.4)A synthetic jet actuator is studied for the prediction of the internal flow field to find out the way of selecting the suitable synthetic jet cavity length and opening width.The speed statistics on key points are collected.The results show that when the Re is1000 and the frequency is 100 Hz,the energy of jet is dissipated at a distance of 60 Da from the center point,so the length of the synthetic jet cavity should be less than 60 Da.The speed during the whole cycle tends to be consistent at 50 Da,indicating that the length setting to 50 Da can ensure that the flow is stable and large.At different distances from the center point,the speed statistics of each point along the radial direction have been collected to find out the region of positive velocity.Setting the region as the outlet width leads to smooth continuous outflow.According to this method,the optimal outlet width at the length of 40 Da is 12 Da.It is proved that this method can be referenced.