大功率多激励源压电陶瓷超声换能器的研究

As an effective solution for industrial applications of many new ultrasonic processing technology, the intervention-type ultrasound processing system has attracted extensive attentions. At present, the traditional longitudinal-vibration sandwich piezoceramic ultrasonic transducers are adopted mostly as sound sources of the existing intervention-type ultrasound processing systems, and the lower power capacity of the traditional piezoceramic transducer limits the large-scale applications of these intervention-type ultrasonic processing systems in industry. In order to meet the urgent demand for the longitudinal vibration ultrasonic transducer with high power capacity, a new-style high-power ultrasonic transducer with multiple sets of piezoceramic elements will be thoroughly studied in this project.The main research contents include the design theory of this transducer, the dependencies between its structure, material and load and its performance parameters, the multi-objective optimization design method of this transducer considering more practical engineering requirements, and the temperature characteristic and nonlinear behavior characteristic of this transducer in different working conditions. These research works will provide the theoretical basis, experimental evidence and technical support for manufacture the stable and reliable high-power ultrasonic transducer with multiple sets of piezoceramic elements.

作为解决众多功率超声处理新技术工业化应用的一种有效方案，介入式超声处理系统受到了人们的广泛关注。目前已有的介入式超声处理系统大多采用传统的纵向振动夹心式压电陶瓷超声换能器作为声源，其较低的功率容量限制了这些介入式超声处理系统在工业中的大规模应用。为满足工程中对大功率容量纵向振动超声换能器的迫切需求，本项目拟对一种新型的大功率多激励源压电陶瓷超声换能器进行系统研究。主要内容包括：研究这种换能器的设计理论；探讨多激励源压电陶瓷超声换能器的结构、材料及负载与其性能参数之间的依赖关系；研究能满足实际工程需要的大功率多激励源压电陶瓷超声换能器的多目标优化设计方法；研究多激励源压电陶瓷超声换能器在不同工作状态下的温度特性及非线性行为特性等。本项目的研究将为研制稳定可靠的大功率多激励源压电陶瓷超声换能器提供理论基础、实验依据及技术支撑。

为满足工程中对大功率容量纵向振动超声换能器的迫切需求，本项目提出一种新型的大功率多激励源压电陶瓷超声换能器并对其进行系统研究。给出了多激励源压电陶瓷超声换能器的等效电路及各参数的表达式，进一步推导出双激励源超声换能器的共振频率方程，为此类换能器的设计提供理论基础。基于Kikuchi等效电路，具体推导出双激励源超声换能器的等效机械阻、力因子及夹持电导的表达式，通过算例数值分析了双激励源压电陶瓷超声换能器的结构、材料及负载对其工作特性的影响，结果显示双激励源换能器在不明显降低换能器综合性能的情况下能有效增加压电陶瓷的体积，因而可大幅提高换能器的功率容量和负载能力，更适用于大功率重负载的场合。采用主要目标法对双激励源压电陶瓷换能器进行了多目标优化设计，根据优化结果制作了若干样机并对其进行大功率测试，结果表明该换能器具有功率容量大、电声效率高、频率稳定性好等优点，保守估计样机中的压电陶瓷在连续大功率工作状态下功率密度可达0.9 W/(cm3•kHz)。研究了压电陶瓷堆位置对夹心式换能器的机械损耗及介电损耗的影响，结果表明压电陶瓷堆的最佳位置与实际负载息息相关，且随着负载的增大最佳位置逐渐逼近换能器的节点位置。对双激励源压电换能器进行了热分析，发现换能器的谐振频率随着温度升高降低，振幅也随着温升减弱，而静态电容随着温度的升高逐渐增大。搭建了压电换能器的大功率测试平台，初步了解了不同功率级下双激励源压电陶瓷超声换能器的非线性特性，实验表明这些非线性行为除了受换能器本身的影响外，也和电匹配及声负载情况息息相关。上述研究工作为该类换能器的工程应用提供了理论依据和技术支撑，也证明通过级联多个半波长换能器以提高整个系统功率容量的想法是可行的，为研制大功率超声换能器提供了一种新思路。