复合型功率超声CYMBAL换能器的研究

Because of its own structure and constituting elements, traditional CYMBAL transducers are mainly used in underwater sound and ultrasonic field where low and medium power is involved. When high power is needed, traditional CYMBAL transducer is not suitable. In this project, a new kind of composite CYMBAL transducer which can be used in fields of high power ultrasound and underwater sound are proposed and studied. The composite CYMBAL transducers are composed of two main constitutive parts, one is the vibration driving system, which is a combination of piezoelectric rings and metal rings (while in the traditional CYMBAL transducer, the vibration driving system is only a single piezoelectric disk or ring), and the other one is vibration (sound) radiating system, which is a complex metal cap with different structures and shapes in flexural and coupled vibration. These two constitutive parts are tightly combined together by some kind of fastening bolts in radial or axial direction. Compared with the connection method of gluing in traditional CYMBAL transducers, the fastening bolt method is favorable in increasing the power of the transducers. First, the radial and coupled vibration of the vibration driving part is studied both analytically and numerically, the electro-mechanical equivalent circuit is derived and the resonance frequency equation is obtained. The relationship between the electric impedance, the resonance frequency, the effective electromechanical coupling coefficient and the mechanical quality factor with the geometrical shape and dimensions is analyzed and studied. Second, different mechanical connection methods between the vibration driving part and the vibration radiating part are studied and compared with each other and the vibrational mode conversion of the radial vibration to flexural vibration is investigated. Third, the complex flexural vibration of the metal caps with different structure and shapes is studied both analytically and numerically. Both the vibrational characteristics and the radiation performance are analyzed. The relationship among the radiation impedance, the acoustic field distribution of the transducer and the vibrational mode, the load impedance, the shape and the dimensions of the metal cap is further studied both analytically and numerically. At last, the optimization design of the transducer is conducted and some composite CYMBAL high power transducers are manufactured and experimented. The electromechanical characteristics and the radiation acoustic field are measured by impedance analyzer, laser scanning vibrometer sound field measuring system and compared with each other.

针对传统的CYMBAL换能器仅适合于中小功率水声及超声应用的问题，本项目提出一种复合型大功率超声及水声CYMBAL换能器。该换能器的驱动部分是由纵向极化或径向极化的压电陶瓷圆盘或者圆环以及等厚度或者变厚度的金属圆盘或圆环复合而成，辐射部分则采用不同形状及结构的弯曲振动辐射体。首先，探讨换能器的解析设计理论，推导其径向振动及径弯振动模式转换的机电等效电路及共振频率方程。探讨换能器的性能参数及振动模态与其结构、形状、几何尺寸及负载的依赖关系，研究换能器驱动部分的径向振动与辐射体弯曲振动之间的最佳耦合方式。利用数值方法对换能器的振动模态、径弯振动模态转换、频率特性及辐射声场进行仿真，给出换能器的弯曲振动位移分布和辐射声场与其振动模态及负载阻抗之间的关系。利用阻抗分析仪、激光测振仪及超声C扫描系统对换能器的机电参数、振动位移及辐射声场进行实验研究，为此类换能器的优化设计提供理论及实验数据。

CYMBAL换能器在水声学、工业超声以及医学超声等领域具有比较广泛的应用。然而，由于结构以及换能器振动模态的限制，传统的CYMBAL换能器仅适合于中小功率水声及超声应用领域。针对这些问题，本项目提出一种复合型大功率超声及水声CYMBAL换能器。该换能器的驱动部分是由纵向极化或径向极化的压电陶瓷圆盘或者圆环以及等厚度或者变厚度的金属圆盘或圆环复合而成，辐射部分则采用不同形状及结构的弯曲振动辐射体。首先，利用严格的解析分析理论，分析探讨了纵向极化或径向极化的压电陶瓷圆盘、圆环以及压电陶瓷圆环晶堆的纵向振动、径向振动及其耦合振动理论，得出了其机电等效电路。在此基础上，推出了换能器的输入电阻抗及共振频率方程。其次，对不同结构及形状尺寸的金属超声波辐射器进行了分析，探讨了变截面金属圆环及圆盘的径向振动和弯曲振动理论，给出了其精确的解析分析理论及机电等效电路。在此基础上，探讨了换能器的性能参数及振动模态与其结构、形状、几何尺寸及负载的依赖关系，得出了换能器的共振频率、反共振频率、有效机电耦合系数以及辐射功率等机电参数与换能器的形状和几何尺寸之间的依赖关系。研究了换能器驱动部分的径向振动与辐射体弯曲振动之间的最佳耦合方式。为了验证换能器解析分析理论的正确性，利用数值模拟方法对换能器的振动模态、径弯振动模态转换、频率特性及辐射声场进行了仿真，给出了换能器的径向振动及弯曲振动位移分布和辐射声场与其振动模态及负载阻抗之间的关系。最后，利用阻抗分析仪、激光测振仪及超声C扫描系统对换能器的机电参数、振动位移及辐射声场进行了实验研究，并与解析理论和数值模拟结果进行了比对和验证。.本项目所研究的复合型功率超声CYMBAL换能器有望应用于水声、医学超声以及工业超声技术领域中，在声纳应用、医学超声治疗、超声降解、超声波采油，超声化学以及超声提取等超声液体处理技术中获得应用。