| Piezoelectric pump is a new type of fluid pump,which utilizes the vibration generated by the piezoelectric actuator directly to make liquid flow in a one-way or produce dynamic pressure.Compared with the traditional pump,the piezoelectric pump has many advantages such as simple structure,small body,no interfering of electromagnetism and easy to control the output characteristics,etc.So it is widely used in aerospace,medical equipment,bio-genetic engineering and other fields.Piezoelectric pump is not a simple miniaturization of traditional pumps,its shape,size and flow characteristics of fluid all have a great impact on the performance.In this paper,the proposed diffiuser/nozzle valve-less piezoelectric pump not only eliminates some in erent defects of piezoelectric pump with valve(such as the rather low working frequency,fluctuating of flow rate with variation of the chamber volume,wear and fatigue of movable components),but also can make the actuator,the drive mechanism and pump body as a whole part,lifetime and reliabijlity of the pump are definitely improved.In addition,it has other advantages such as compact structure,low fabrication cost and easy miniaturization.In order to investigate the flow pattern inside the piezoelectric pump,the contents and conclusions of this paper mainly include the following aspects:1.A brief overview of the micro-pump based on the micro electro mechanical systems(MEMS)was done and the present condition in domestic and abroad and the development in the future of piezoelectric micro-pump are summarized.2.The basic theory of micro fluid was introduced,and the flow characteristics of micro-pump were analyzed theoretically,and the expression of theoretical flow rate and ratio coefficient of flow resistance was given.3.Based on the piezoelectric theoretical knowledge,the theoretical expression of the deformation and natural frequency of circular piezoelectric oscillator was deduced,vibration analysis was done to the circular single-chip piezoelectric oscillator driven by sinusoidal voltage using the finite element analysis software ANSYS and the factors were found which can affect the amplitude of the center of the piezoelectric oscillator.It was studied that the different effects resulted from the variety base materials and structural parameters for the amplitude of the center of the piezoelectric oscillator.It proved that under the condition of simple support if the substrate material was made of copper,and the radius ratio of piezoelectric film and substrate was about 0.7,larger deformation would be obtained.The thinner thickness of PZT or the bigger of excitation voltage was,the larger deformation may be obtained.The study supplied theoretical basis and reference value for optimizing on the structure of the piezoelectric actuator and improving its performance.4.The mathematical model of the diffuser/nozzle was established.Through the finite element method analysis to the flow channel by the software of ANSYS CFD,the curves of the distribution of velocity and pressure were obtained.Besides,it was discussed that the different effects results from structural parameters for the ratio coefficient of the flow resistance.The dynamic characteristics of the piezoelectric oscillator were programmed by C program language,transferred into FLUENT,and combined with the dynamic grid technology,the numerical simulation was carried out by indirect coupling method to obtain the internal flow field characteristics of the pump.The influence of driving frequency,amplitude(voltage)and other factors on the pumping function was studied.The results showed that the maximum flow rate can be obtained when the load frequency was 400 Hz.The larger the voltage was loaded,the greater the flow rate could be acquired.It provided a useful reference for optimizing and designing the piezoelectric pump. |
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