面向热声制冷系统的微型磁致伸缩换能器基础问题研究

The primary problem that restrain the thermoacoustic refrigerator miniaturation is the lack of adequate strength and stability of high performance miniature sound driver, and the high performance heat exchanger located at the end of thermoacoustic stack both. To solve this problem, this topic proposed the magnetostrictive transducer as thermal acoustic actuator. With numerical simulation and experimental method, some basic problem occurred in the process of high power high frequency magnetostrictive miniaturization will be studied. and this paper will discuss the new problems and new phenomenon、new rules about the actuator. perfecting the relevant theory, further explore improving micro magnetostrictive actuator energy density of radiation and radiation efficiency way are important work of this task, meanwhile, some new sturcture and method to restrain generate heat and increase the cooling effect will be discussed also. The main research contents include: Looking for ways to improve the micro magnetostrictive actuator’s radiant panel amplitude, while increase the radiation intensity and power density, and to explore the conditions under which a thermoacoustic alternating flow can be inspired in working medium; coupling mechanism between acoustic radiation plate and working medium, through analysing of the influence factors of the impedance, achieve the best impedance matching; Study the effect of radiant panel amplitude and frequency on sound pressure ratio, thermoacoustic resonator geometry optimization and structural parameters optimization and determination of the energy-gathered resonance tube, and magnetostrictive actuator heat dissipation problem; Study the corresponding matching relations between magnetostrictive actuator working frequency and thermoacoustic frequency, etc. .Baotou Rare Earth Institute has developed T-D stick with the method of bonding T-D material powder, under 5kHz alternating current drive condition，the stick can work continuously at room temperature, stretching coefficient could reach to pure T-D metal's 1 / 3. Inner Mongolia University of Science and Technology is located in the hometown of Baotou Rare Earth, to carry out the research, not only for promoting the development of sound theory and the thermoacoustic refrigeration technology advances has practical significance, but also to promote the application of rare earth functional materials and devices has strategic significance, while the region's economic development also has a significant stimulus.

目前制约热声制冷机微型化的首要问题是缺乏强力且性能稳定的高频微型声驱动器和高效的板叠冷热端换热器。针对此问题，本课题拟采用磁致伸缩换能器作为热声驱动器，用数值模拟和实验的方法对大功率高频磁致伸缩换能器微型化过程中出现的若干基础问题展开研究工作，探讨新问题、新现象、新规律，完善有关理论，进一步探索提高微型磁致伸缩换能器能量辐射密度和辐射效率的途径，同时研究抑制发热和提高散热效果的结构与方法。主要研究内容包括：寻求提高微型换能器辐射板振幅的途径，在提高辐射强度和功率密度的同时，研究能激励出热声介质交变流动的条件；研究在高强声波下辐射板与工质的耦合机制及阻抗影响因素，实现最佳阻抗匹配；研究辐射板振幅和频率对声压比的影响、热声谐振腔几何结构的优化、聚能型谐振管最佳结构参数的确定和换能器的散热问题；研究辐射频率和热声频率的对应匹配关系等。内蒙古科技大学地处稀土之乡包头，开展该课题研究，不仅对于推动声学理论的发展和热声制冷技术的进步具有科学价值，更对促进稀土功能材料应用器件的开发研究和拓宽稀土材料应用领域等具有战略意义。

当前制约热声制冷机微型化的首要问题是缺乏足够强力且性能稳定的微型声驱动器,实际声驱动器均不同程度地存在驱动力不足和辐射效率偏低等情况，包括压电陶瓷换能器。因此，在高频大功率驱动器的开发应用、谐振腔几何结构/管型优化、辐射板与工质耦合机理的揭示、驱动器辐射效率的提高等方面开展基础研究可以推动热声制冷机微型化的进程。. 本课题针对以上问题，以磁致伸缩换能器作为热声驱动器，用数值模拟和实验的方法对大功率高频磁致伸缩换能器微型化过程中出现的若干基础问题开展了研究工作，探讨了把磁致伸缩换能器用于热声制冷机的可行性和效果。主要研究内容包括：换能器总体结构参数的确定、提高辐射板振幅的结构形式、换能器辐射板与工质的耦合条件、提高制冷机谐振腔内声场强度的方法、辐射板形状对谐振腔内声场分布的影响、热声谐振腔几何结构的优化、聚能型谐振管最佳结构参数的确定和换热器与板叠的连接方式、热声制冷机板叠内气体的微观热力循环模型等。. 课题研究在T-D铁合理利用方面取得了新进展，用Atila软件分析了综合考虑T-D棒E效应及跳跃效应时T-D 的幅频特性，为T-D材料的应用提供了更准确的依据和分析方法。这一工作填补了该领域内的研究空白。.课题研究了激励方式对谐振腔内声场强度的影响，为在谐振腔内产生、维持高亮度单色驻波找到了有效的方法。这一方法对提高热声制冷机效率具有良好的应用前景。. 在磁致伸缩换能器结构设计方面，完成了磁致伸缩换能器辐射板位移放大机构设计，利用柔性铰链的无机械摩擦、"无间隙"运动灵敏度高的特点，设计了基于柔性铰链的磁致伸缩换能器辐射板位移放大机构，并运用有限元软件对微位移放大机构的整体放大倍数进行了有限元分析、评估。该放大机构申报了专利，发表了相关论文，为相关设计应用提供了参考。.此外，对热声制冷机板叠内气体的微观热力循环进行了理论探讨，通过对驻波型热声制冷原理的深入研究，预测了在驻波型热声制冷机谐振腔内的板叠上可形成轴向冷热交替分布的温度状态。.　　最后用扬声器代替磁致伸缩换能器，进行了热声制冷实验，取得了取得温降６度的效果，加深了对热声制冷问题的认识，为下一步工作打下基础。