纵径耦合多频夹心式压电功率换能器的研究

In this project,we proposed a new type of longitudinal-radial coupling multifrequency sandwich piezoelectric power transducer. The radial composite piezoelectric transducer consists of metal circular tube and radial polarization piezoelectric ceramic pipe. It's longitudinal size close to diameter size. Firstly, using analytical method based on the apparent elasticity principle,the electromechanical equivalent circuit of the longitudinal radial vibration mode is obtained.Then, the resonance frequency equation of the transducer is also obtained. The relationship between the resonant frequency and the geometry size will be studied, at the same time, the relationship between effective electromechanical coupling coefficient and the geometry size will be studied. Secondly, the transducer vibration modal is studied by using numerical simulation mothod. The relationship between frequency characteristic and geometric sizes is discussed. The performance parameters and the parameters optimization in different frequencies are discussed in order to realize transducer working in multiple frequence ang high power condition. Thirdly, the transducer will be designed and machininged according to theoretical calculating results. The frequency characteristics, load characteristics, displacement, the acoustic field distribution of the transducer will be tested and analyzed. The optimized design scheme of the power transducer will be proposed based on the numerical analysis and experimental results. The expected research results will be innovation and perfection for design theory of the transducer, and will establish a theoretical basis for this kind of transducer's design. Meanwhile, the research results will has a promotion effect for developping the new ultrasonic techniques.

本项目提出一种新型的纵径耦合多频夹心式压电功率换能器，该换能器由纵径尺寸接近的金属圆管与径向极化的压电陶瓷圆管在径向复合而成。第一，从表观弹性法原理出发，用解析法研究得出各组成部分做纵径耦合振动的机电等效电路，进而得到该换能器机电等效电路及共振频率方程。探讨换能器的谐振频率、有效机电耦合系数等与几何尺寸间的相互关系。第二，利用数值法,对换能器的振动模态进行数值模拟和仿真,探讨耦合振动频率特性与其几何尺寸相互关系，对换能器在不同频率下的性能参数进行探讨及优化,以期实现换能器多频及大功率辐射。第三，设计加工换能器，对换能器的频率特性、负载特性、位移、声场分布等进行测试和分析；综合解析、数值分析及实验结果，得到实现多频大功率换能器的优化设计方案。本项目研究成果相对于传统的换能器设计理论是一个完善和革新，为此类换能器的设计奠定理论基础，对超声新技术的发展具有推动和促进作用。

为克服传统纵向夹心式换能器共振频率单一难以调整，不能实现能量的空间辐射等缺点，提出了一种新型结构的换能器，该换能器由径向极化的压电陶瓷圆管和内外金属圆管在径向复合而成，本项目主要对换能器的振动特性进行了研究，主要的工作有：.（1）采用表观弹性法分析纵径尺寸接近的金属圆管，获得金属圆管耦合振动的机电等效电路和频率方程，并对金属圆管耦合振动特性进行仿真分析，获得在纵向与径向产生强烈耦合振动的条件。.（2）采用表观弹性法研究纵径尺寸接近的压电圆管，获得耦合振动的机电等效电路和频率方程，得到几何尺寸与频率、有效机电耦合系数间的相互关系，模拟仿真了压电管的耦合振动，研究发现：压电管的管壁厚度和纵径尺寸比对耦合振动的振动特性影响较大。.（3）将换能器各组成部分的机电等效电路在径向相连，得到耦合振动换能器的机电等效电路，从而推导出共振与反共振频率方程，由此得到几何尺寸与共振、反共振频率以及有效机电耦合系数间的关系：当压电圆管在换能器的径向尺寸比例增加，共振、反共振频率减小，有效机电耦合系数增大；当换能器的纵向径向尺寸比(h/d)增大，共振反共振频率减小，有效机电耦合系数在h/d等于2附近有一拐点。设计、加工径向夹心耦合振动换能器，对其振动特性进行测试，理论计算、数值仿真、实验测试结果比较一致。研究表明：纵径尺寸接近的径向夹心换能器产生耦合振动，可实现多频大功率辐射，当h/d等于2.5附近耦合振动最剧烈。.该换能器结构简单，对传统换能器是一种创新，对于发展新型的超声换能器、改善现有超声技术的应用效果、开发新应用领域具有理论指导意义和实际应用价值。