【作者】 张春萍；

【导师】 刘伟； 郭方中；

【作者基本信息】 华中科技大学 ， 制冷及低温工程， 2011， 博士

【摘要】 本文的课题是在多项科学基金的资助下完成的,以高频热声装置的微型化为研究背景,以热声核为研究对象,在分析了热声核的特性参数和网络参数的基础上,提出了采用特征时间来作为分析和评价热声系统的性能指标,以便于指导和分析热声系统的理论研究和设计工作。通过对高频热声制冷机及其外激励装置微型化的设计和性能实验测试,从理论和实验两方面来探索提高热声装置的效率和实用化的优化方法。主要工作内容包括以下几个方面：首先通过对热声核的参数激励原理的分析,指出热声核子系统符合三频率参数网络模型,热声效应中能量的反馈和增益来自于不同频率的耦合,因此热声核的频率特性是影响热声效应的重要参数。随着频率的提高,系统的尺寸变小,其空间尺度和时间尺度已经可以与系统的动态过程时间相比,此时把系统的特征时间ωOτTA即热声弛豫时间和频率的乘积一起作为衡量热声效应的一个指标,可以有效的评价热机系统的工作性能,通过采用Zuber的时变率相似分析方法进一步验证了这个指标的可行性,其有助于简化以往用于热声系统的复杂的分析方法。其次,鉴于热声核在热声热机中的重要地位和作用,正确的设计和选择高效率的热声核就成为热声热机设计中的关键一步。由于不同热声核与同一谐振管匹配后的频谱特性不同,导致其对频率的选择性不同。通过对二者匹配后的频率特性进行实验辨识,比较了五种不同类型热声核填料的复流容,在此基础上,以品质因数为评价指标对这五种热声核的性能进行了对比,以此作为优选不同热声核与谐振管匹配的依据。第三,采用系统辨识的方法是分析热声核中的复杂流动关系的一个简化而有效的手段,在建立热声核子系统网络模型的基础上,利用参数辨识技术对热声核在两种不同长度谐振管中的网络参数声阻、声感和声容分别在加热和不加热的情况下进行了实验辨识,并与理论计算结果进行了对比分析,初步验证了系统辨识方法可用于热声系统的参数辨识。第四,较高的频率使得热声热机的整体尺寸较小,因而要求与其配合使用的所有装置的尺寸也都比较小,同时,不降低其工作性能指标。结合热声热机的实际特点和工作要求,对热声热机的外激励驱动装置进行了微型化的优化设计,以动磁结构为基本形式,设计并计算了内外两种磁路结构；以改进后的柔性蜗旋弹簧组件作为悬吊结构,对比了型线改进前后的相关性能指标；利用弹性材料和结构设计来调整整机中各部件的同轴度,以有效提高动磁激振器的使用寿命,在此基础上,设计了内磁路结构形式的动磁激振器,以替代效率不高的扬声器作为热声制冷机的驱动装置。第五,谐振管的形状对于热声热机的性能有一定的影响,通过对圆形截面和扁形截面的两种谐振管进行静态模拟计算分析,提出可以通过优化谐振管的截面来获取高振幅的声场。此外,对于高频的热声制冷机,鉴于可借鉴的设计经验比较少,为了尽快实现可实用化的目的,设计并加工了一台小尺寸的风冷式热声制冷实验样机,以制冷温降为性能指标,进行了实验验证,并对实验中发现的问题进行了分析。更多还原

【Abstract】 This research was supported by several science and project foundations which focused on the studies of high frequency thermoacoustic engine. Based on the analysis of characteristic and network parameters of thermoacoustic core, the characteristic time was used to evaluate the performance of thermoacoustic core in order to simplify the theory study method and instruct the engine design work. Through the design process and experimental performance test on the high frequency thermoacoustic refrigerator and its external excitation device, the optimizing experience could be achieved from theory and reality. The following were the main work:At first, basing on the analysis of parameter exciting principle, the network of the thermoacoustic core was conformed to a three-frequency parameter. The coupling of different frequencies was devoted to the energy gain and feedback. So it was the frequency who decided the ability and efficiency of the thermoacoustic effect in the engine. With the rising of the frequency, the size of the thermoacoustic engine would become smaller and smaller. The characteristic space and time dimensions were comparative with the time of system dynamic process. Then the relaxation time and frequency together could be used to scale the thermoacoustic effect. By the help of Professor Zuber’s fractional scaling analysis, the characteristic time was proved to simplify the current theory research on thermoacoustic system effectively.Secondly, the thermoacoustic core was should be designed and chose correctly and effectively for its import role on the thermoacoustic effect. Since different thermoacoustic cores had different frequency properties, they had different frequency choices in the same resonator. Then by the experimental identification on the frequency characteristic of five kinds of thermoacoustic core coupled with the same resonator, the complex compliance and quality factor of these matrixes were experimentally analyzed respectively in the system of loudspeaker-driven thermoacoustic resonator (TAR). And the quality factor was then used to evaluate the performance of the thermoacoustic core to study the matching relationship with the resonator. Thirdly, the system identification method could help to analyze the complicated flow phenomena of gas whin the theromacoustic core. After setting up the network model of thermoacoustic core, the parameter identification skill was used to identify the network parameter of thermoacoustic core experimentally. The resistance, inertance and compliance were identified in two kinds of length resonator with and without temperature gradient and compared with the theory results to test and verify the feasibility of the system identificationFourthly, the high frequency made the size of thermoacoustic engine and external exiting device small without performance reduction. After consideration the requirement of thermoacoustic engine, a miniature moving magnet actuator was designed and made to drive a small thermoacoustic refrigerator. Two kinds of magnet configuration was designed and calculated for different application. The line of spring was improved and its static load was simulated and compared with the unimproved one. The concentricity of the whole engine was designed to be adjusted through the frame.At last, the shape of the resonator had some influences on the thermoacoustic engine. By simulating two kinds of cross section resonator, the performance of circular and flat tube was compared and analyzed. The result showed that the flat tube could improve the sound field in some degree. Furthermore, a high frequency thermoacoustic refrigerator was made to investigate experimentally its refrigeration performance and accumulate the miniature engine experience.更多还原