【作者】 康慧芳；

【导师】 李青；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 制冷及低温工程， 2009， 博士

【摘要】 随着热声研究的发展,为了提高热声转换效率,热声热机从驻波型发展到行波型。然而,实际热声热机系统不可能工作于纯行波或纯驻波模态,而是工作于行驻波模态。到目前为止,大部分研究者在研究热声热机时,仍基于行波或驻波的分析,极少有从行驻波的角度对实际热声系统中行驻波模态进行研究,更没有基于行驻波分析的热驱动热声制冷机的研究。正是因为这样,本文开展了行驻波型热驱动热声制冷机的理论和实验研究,以全新角度去认识和研究热声热机:基于波动理论,从行驻波的角度深化热声学的理论研究,提炼出了新的无因次参数,提出了行驻波热声效应的分析方法和回热器综合优化的方法,进一步丰富和完善了热声理论。基于优化分析的结论,提出并研制了行驻波型热驱动热声制冷机,推动热声热机的发展。为此,开展了以下几个方面的理论和实验的研究工作:1.对现有的线性热声理论进行了总结分析,并引入行驻波的概念,对热声热机声场进行行驻波分解。在此基础上,权衡速度、精度和易于使用等条件开发了“小振幅热声热机可视化仿真软件”,并使用该软件建立了行驻波型热驱动热声制冷机的数值模型。然后对行驻波型热驱动热声制冷机的回热器、热缓冲管、声功回收管和谐振管等元部件的结构参数以及系统的运行参数进行了优化计算。2.基于波动理论,对声场进行行驻波分解,给出了行驻波声场关键参数的无量纲表达式,提炼出了声场特性集成化参数。该集成化参数是声场中的关键参数(振荡压力、振荡速度、特征声阻抗、压流相位差和时均声能密度)集成化的体现,同时也反应了各个声场中关键参数之间的相互关系。结合这两个集成化参数,分析了行驻波声场的分布特性,分析表明,随着行波成分的增加,虽然行波相位区长度增加,但是行波相位区当地声阻抗减小。因此,在设计热声热机时,应综合考虑行波相位区的长度和行波相位区的阻抗来选择合适的行波比率。另外,在行波比率相同的行驻波声场中,时均声能密度各处相等。3.为了分析行驻波声场中的热声效应,提出了两种分析方法:数学公式分析和定性分析。两种分析方法的结论一致:对于热声发动机,为了提高声功增益和效率,回热器高温端应该靠近压力腹点,并且行波传播方向与温度梯度方向一致,使得发动机回热器中行波成分和驻波成分均实现热到声的转换;对于热声制冷机,为了提高制冷量和制冷系数,回热器高温端应该靠近压力腹点,并且行波传播方向与温度梯度方向相反,使得制冷机回热器中行波成分和驻波成分均将热量由低温端泵送到高温端。4.根据对行驻波声场中热声效应的分析,在国际上首次提出了一种行驻波型热驱动热声制冷机系统:该系统包含一个热声发动机和一个热声制冷机,前者为后者的驱动源。发动机和制冷机均位于一个环形圈中,并与一个谐振管相耦合,其优点为:(1)有效利用了声波中行波成分和驻波成分共同作用的热声效应;(2)由发动机产生的声功直接进入制冷机进行泵热;(3)使用声功回收管和声功反馈管将制冷机使用后的残余声功,反馈到发动机进行再次利用;(4)发动机和制冷机布置在同一个环形圈内,并且环形圈耦合谐振支路的结构使系统总长接近1/4波长,有效的减小了系统长度,使系统结构紧凑。研制的高频行驻波型热驱动热声制冷机总长不到1m,在以氦气为气体工质,充气压力为2.2MPa,工作频率为234Hz,加热量为300W时,实现了-30°C的无负载温度,并且在0°C时可以提供40W的制冷量。5.从基本热声公式出发,提炼出了行驻波声场参数、回热器结构参数以及热声热机性能参数的无因次表达式,并通过这些无因次参数的分析,结合声场集成化参数,提出了一种综合优化热声热机的全新的优化分析方法。该方法结合了回热器结构参数和声场参数,并考虑了各个参数之间的相互制约关系,对热声热机的性能进行了全面的优化分析。分析结果能帮助理解已存在热声热机的最优实验工况,同时对设计新型热声热机提供了理论指导。更多还原

【Abstract】 Thermoacoustic research has progressed steadily over decades. To improve the thermoacoustic efficiency, the thermoacoustic devices have evolved from the standing wave devices into the traveling wave devices. However, a real regenerator operates on neither pure traveling wave mode nor pure standing wave mode. Therefore, so far, most researchers still focus their particular attentions on the traveling wave or the standing wave when they design their thermoacoustic devices, and few published literatures have studied on the traveling-standing wave. Therefore, this thesis investigatie the theory and experiement of the thermoacoustically driven thermoacoustic refrigerator based on thermoacoustic analysis in the traveling-standing wave, and understand the thermoacoustic device from a new view. Based on the wave theory, this thesis developes the thermoacoustic theory by traveling-standing wave view, abstracts some new normalized parameters, proposes analysis methods of thermoacoustic performance in traveling-standing wave, and presents a novel optimization method of the regenerator. This enriches and consummates the themoacoustic theory. Based on the optimization analysis, a novel thermoacoustically driven thermoacoustic refrigerator based on thermoacoustic analysis in the traveling-standing wave is proposed and investigated, which develops the themoacoustic device. In this thesis, progresses are made as follows:1. This thesis summarizes and analysizes the liner thermoacoustic theory, introduces the concept of the traveling-standing wave, and then separates the traveling-standing wave. Based on this, combining the merit of the existed software and the new technology of thermoacoustics, and try to compromise among speed, precision and facility, a new computation software of thermoacoustic device was wrote. Then, a theoretical model of high frequency thermoacoustically driven thermoacoustic refrigerator was set up, and the oscillation pressure, oscillation flow rate, the phase difference, temperature and the time-averaged energy flux in the engine was analyzed, which make the acoustic distribution clearer. And then, optimize these thermodynamic components (e.g. the regenerator units, thermal buffer tube, compliance cavity, feedback inertance, and recycling inertance) carefully by this software.2. Based on the wave theory, this thesis separates the traveling-standing wave, obtains normalized expressions of some key parameters about the acoustic field, and abstracts two integration parameters. The two integration parameters can representate the characterization of the key parameters in the acoustic field, such as the time averaged acoustic energy density, the osocillation pressure, the osocillation velocity, the specific acoustic impedance and the leading phase of pressure to velocity, and include their relationship. Then analyzed the acoustic field characteration by the two integration parameters. It is pointed out that, with increase of the travelling wave componet, although, the length of the travelling wave phase region increases, the specific acoustic impedance in the travelling wave phase region decreases. Thus, the specific acoustic impedance and the length of the traveling wave region should be considered in the designs of new thermoacoustic devices, synthetically. Accordingly, the time averaged acoustic energy density is independent of the position in the acoustic field. Thus, the time-averaged acoustic energy density is also the time-spatial averaged acoustic energy density.3. To study the thermoacoustic performance in traveling-standing wave, two analysis methods are presented: the mathematical formulation analysis and the qualitative analysis. It is found that the results of the two methods are consistent. For the thermoacoustic engine, in order to gain a better acoustic power and efficiency, the hot end of regenerator should be close to the pressure antinode, and the traveling wave component should propagate from the hot end to the ambient end. For the thermoacoustic refrigerator, in order to gain a better cooling power and coefficient of performance, the ambient end of regenerator should be close to the pressure antinode, and the traveling wave component should propagate from the ambient end to the cold end.4. Acoording to the thermoacoustic performance in traveling-standing wave, a novel thermoacoustically driven thermoacoustic refrigerator has been originally proposed in this paper. It consists of a thermoacoustic engine and a thermoacoustic refrigerator, and the former is the driving source of the latter. Both the engine and the refrigerator are located in one loop tube coupled with a resonator tube. Compared with the other types of the heat driven thermoacoustic refrigerators, this device has the merits: (1) It effectively utilize the thermoacoustic performance of the combined action of the traveling wave component and the standing wave component; (2) The acoustic power produced by the thermoacoustic engin is used to drive the thermoacoustic refregenerator directly; (3) The feedback tube realizes the recycle of the residual acoustic power out of the thermoacoustic refregenerator. On the basis of the analysis and consideration, a miniature high frequency thermoacoustically driven thermoacoustic refrigerator besed on traveling-standing wave was built firstly in the world. The total length of this refrigerator system is less than 1 m. At the operating point with the mean pressure of 2.2 MPa, helium as working gas, frequency of 234 Hz, and a heating power of 300 W, the experimental refrigerator provides a no-load temperature of -30°C and a cooling power of 40 W at the cooling temperature of 0°C.5. Based on the linear thermoacoustic theory, the normalized expressions of acoustic parameters, regenerator parameters and the thermoacoustic performence parameters are derived and calculated, and then proposed a novel synthetical optimzation method for thermoacoustic device. Some conclusions have been obtained, which are of significance to explain the optimum work conditions of existing engines and to guide the designs of new thermoacoustic devices.更多还原