| Piezoelectric pump is a machine which uses the inverse piezoelectric effect of piezoelectric material to convert the input electrical energy into mechanical energy to make the fluid motion.Piezoelectric pump has the advantages of simple structure,low power consumption,no electromagnetic interference,precise output,rapid response and high compatibility.It has been widely used in biological gene detection,live cell transport,drug supply,chip heat dissipation and other fields.It has become an important tool of microflow transport and an important component of microfluid control technology.Unidirectional fluid transportation is the focusing at Present of piezoelectric pump,however,it is difficult to meet the needs of the development of the industry only with the single function of the unidirectional fluid transportation.There is an urgent need to find a multifunctional mechanism that can bi-directional fluid transportation.Thus derived a variety of piezoelectric pump structure,according to the pump to the conversion mechanism researchers divided it into valve conversion type bidirectional piezoelectric pump and frequency conversion type bidirectional piezoelectric pump.Valve conversion type bidirectional piezoelectric pump control pumping direction conversion according to the principle of the valve body,its pump conversion is easy to realize,but due to the principle of the valve body,there is a lag,and the control is not accurate enough.The frequency conversion bidirectional mechanism is based on the change of pumping direction caused by the change of frequency.The piezoelectric vibrator can respond quickly and switch the pumping direction with the change of frequency.However,the traditional valveless pump is designed for specific function,only for a certain application scenario limits the versatility of valveless pump and the development of multi-scenario application.In view of this,This paper presents a valveless piezoelectric pump with bidirectional variable section flow tube,which based on the difference of local resistance loss of flow tubes with abrupt and gradual cross sections under the influence of fluids with different Reynolds numbers.It produces different flow fields at different frequencies,making the direction of pumping in turbulent flow field opposite to that of pumping in stable flow field.The pumping characteristics of the stable flow field induced by high frequency can be applied to the transport of biological fluids.The turbulent flow field generated by low frequency excitation combined with the two-way pumping capability can drive and mix biological solutions in the detection area,and also serve for the separation and extraction of biological molecules such as antigenantibody detection and immune detection.The valveless piezoelectric pump with variable section of four-flow tube can effectively improve the pumping flow and realize two-way pumping,integrating multi-function and multi-application scenarios.This study is carried out from the aspects of structural design and theoretical analysis,simulation analysis and experimental research and structural optimization.The research content is as follows:(1)Designing the structure of the valveless hydraulic pump with variable section and analyze it theoretically.We designed a variable section structure of four-flow tube based on the difference theory of flow resistance loss between the mutant flow tube and the gradual flow tube.Combined with the influence of the relationship between Reynolds number and conical flow tube parameters on flow resistance.We analyzed the pressure loss at the different sections of each flow tube,determined the positive and negative flow resistance loss and deduced the positive and negative flow resistance loss formula and the output flow formula.It is proved that it is bidirectional in the abstract.(2)This paper introduces the working principle of variable-section valveless piezoelectric pump with four-flow tube and analyzes the flow field of the channel and pump chamber by finite element method.We introduce the motive theory of inverse piezoelectric effect.The velocity transient simulation is carried out at different frequencies to verify the flow resistance difference effect of the valveless pump with variable section of four-flow tube.The velocity flow diagram of suction range and scheduling within a week was obtained through simulation,By comparing the simulation results at different frequencies,the bidirectional characteristics are proved from the perspective of simulation.(3)Relevant experimental studies were carried out.We made a prototype by 3D printing technology,built an experimental platform,carried out amplitude experiment on piezoelectric vibrator,and carried out output pressure test and output flow experiment on valveless pump with variable section of four-flow tube.We conducted an observation experiment on the flow field of the pump chamber,used a high-speed camera to track the flow trajectory of the microsphere in the pump chamber,and explored its flow trajectory in the flow field.(4)We explored the influence of different flow tube structural parameters on the output flow of a valveless pump with variable section of a four-flow tube,obtained the change of different flow tube structural parameters on the output flow of the pump,analyzed the influence of changing parameters on the output flow of the pump,so as to obtain a better output flow performance of the structure. |
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