Investigation On High Frequency Thermoacoustically Driven Thermoacoustic Refrigerator Besed On Traveling-standing Wave

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.