【作者】 梁鑫；

【导师】 王文；

【作者基本信息】 上海交通大学 ， 动力工程及工程热物理， 2017， 硕士

【摘要】 微流动系统作为微型机械(MEMS)领域的重要分支,是微型制冷系统不可缺少的环节。设计与微型制冷系统相匹配压力和流量的微型压气机成为微型制冷系统中的核心与重点。由于压电晶体具有响应快、能耗低、体积小以及能量效率高等优势,在冷却电子芯片温度的微型制冷系统压气机驱动器的研究上有重要的应用。本文从理论上研究压电片驱动薄膜和压电堆压气机的运行机理,比较两种驱动方式的差异。从理论、模拟以及文献实验分析电压、压电与薄膜半径比以及压电厚度与薄膜厚度对压电驱动器横向位移的影响,并通过优化参数提高压电驱动器横向位移和降低压电驱动器共振频率。在此基础上,从理论上探究压电堆压气机共振压气模型和共振压气的工作流程。即当电压频率与压电堆压气机本身共振频率一致时,探究压电堆压气机的振子位移、腔内极限气体压力和输气流量。分析质量块质量、气体压力对压电堆压气机共振频率的影响。比较共振时不同输气压力下质量块位移和气体最大压比的大小。建立压电堆压气机的工作模型,分析压电堆压气机质量块位移和腔体内气体压力随时间的变化关系,得到不同工况下共振型压电堆压气机压力-流量曲线。计算不同工况下共振压电堆压气机的制冷量。表明共振压电堆压气机能满足微型制冷的要求。论文主要研究内容如下:(1)将圆形薄板理论和压电本构方程相结合,在符合Maxwell静电场的电学方程下,分析圆形压电驱动器不同半径处的应力和力矩,得到压电驱动器位移的解析式。并将理论、模拟和文献实验结果对照,发现结果偏差不超过10%,论证理论模型可行(2)分析讨论了电压、压电与薄膜半径比以及压电层厚度和弹性层厚度对压电驱动器横向位移的影响。得出压电驱动器的横向位移与电压的线性变化关系,当压电和薄膜厚度一定时,存在最优压电与薄膜半径比,使压电驱动器位移量最大(本文最优半径比为0.75),压电层厚度和薄膜厚度均会影响压电驱动器的位移,但压电厚度还影响场强分布,故对压电驱动器横向位移影响更大。当压电厚度占总厚度0.45-0.48,压电驱动器横向位移最大(3)用特征值法计算压电驱动器的共振频率,通过理论和实验研究不同压电与弹性半径比和不同弹性膜厚度对压电驱动器的共振频率影响(4)不同于压电液体泵,考虑气体压力对压电堆压气机横向位移附加作用的前提下,建立压电堆压气机动力学模型。分析系统质量和气体压力对压电堆压气机共振频率的影响。通过理论和文献,发现系统共振频率随着气体压力增加而增大和随着质量增加而减少。保证压气结构几何尺寸和共振频率不变的前提下,质量增益/气体压差为3.3。输气压力增加后,系统共振频率随之增大,共振下质量块位移越小,最大气体压缩比越小。(5)建立压电堆压气机的工作模型,分析不同电压和不同频率下,压电堆压气机中质量块的位移和腔内气体的压力随时间的变化。得到压电堆压气机压力-流量曲线。计算不同制冷工况下制冷剂的压力和流量需求。发现共振频率下压电堆压气机能满足微型制冷系统的压力和流量要求。更多还原

【Abstract】 As an important part of the Micro-electro-mechanical system,Micro flow system has been the essential component of Micro refrigeration system.Piezoelectric acutators have been extensively studied in the fields of biological fluid handling、thermal management of electric component and aerospace fields,because its advantages such as fast response,low power consumption,small size and high energy density.More and more scholars have been researching on it.Through the mathematical methods,the operating mechanism differences of piezoelectric membranes and piezostack micropumps are discussed.The impacts of the voltage,the radius ratio and the thickness of piezoelectric and elastic layer on the displacement of circular piezoelectric diaphragm are also investigated.By analyzing the influence of different parameters,the structure design of a circular piezoelectric actuator is optimized and the resonant frequency of a piezoelectric actuator is also decreased.Besides,a resonant piezostack driven gas micropump is researched on the different voltages and frequencies、mass and pressure loads.In the end,the operation model of piezostack micropumps is built to analysis the displacement and the pressure varing with the time.The pressure and mass flow of the piezostack micropumps can be calculated by theoretical model.Through the theoretical analysis,the resonant gas micropump can satisfy the pressure and the mass flow of micro refrigeration system.The main works of this study are as following:(1)Combined with the theory of circular plate and piezoelectric constitutive equation.The analytical model for piezoelectric actuators has been established by analysis strain and bending moment in the different radius of piezoelectric actuator and the analytical solution for membrane deformation is also provided.The results are compared with literature experiments and simulations on the same geometric parameters and material properties.The relative error is less than 10%,from which the analytical model is validated(2)The effect of different parameters on the deformation of piezoelectric actuator has been analyzed.The displacements of circular piezoelectric actuator linearly varies with the voltages.When the thickness and the material property are fixed and the radius ratio of piezoelectric layer and elastic layer is 0.75,the center displacement of circular piezoelectric actuator obtains the maximum.The thickness of piezoelectric layer and elastic layer has different effect on the deformation of piezoelectric membrane.Especially the thickness of piezoelectric layer.When the thickness of the multi-layer is fixed,the optimal thickness ratio of piezoelectric layer and elastic layer is 0.45-0.48(3)The characteristic value method is used to calculate the resonant frequency of piezoelectric actuator,combined with the results of theory and experiment,the effects of the radius ratio of piezoelectric layer and elastic layer and the thickness of elastic layer to resonant frequency are also discussed.(4)When the gas pressure is taken into the dynamic model,a new analytical model of piezostack driven gas micropump is established to discuss the effect of gas pressure to the dynamic system.The pressure of gas has strongly effects on the performance of piezostack driven gas micropump.Combined with the results of theory and literature experiment,the resonant frequency is increased with the gas pressure raise and decreased with the mass increases.To ensure that the resonant frequency is the same,the mass gain/gas pressure difference is 3.3,the magnification of the mass displacement and gas pressure rise radio is also decreased with the increased gas pressure.(5)The operation model of pizostack driven gas micropump is built to analysis the displacement of the mass and the gas pressure varying with time under different voltages and different frequencies.In particular,it focuses on the pressure rises and mass flow of the resonant gas micropump.Compared the performance of piezostack driven gas micropumps with the different voltages and the different frequencies,resonant gas micropump can provide the suitable pressure and mass flow to satisfy the requirements of micro refrigeration systems.更多还原