中文摘要：

环路多级热驱动制冷系统因结构紧凑、潜在效率高等优点在天然气液化及再冷凝方面有良好应用前景。本文提出一种能实现声功多级放大的环路热驱动制冷系统，在天然气液化温度下能够获得千瓦级冷量及较高的热致冷转换效率。基于经典热声理论对三单元环路系统展开了数值模拟。首先，考察了优化结构下声功的沿程分布。接着，将该结构与多脉管结构进行对比。结果表明，前者不仅具有结构简单，冷量方便获取等优势，同时也能获得与后者相媲美的系统性能。此外，进一步考察了谐振管面积比、谐振管长度、加热温度等重要参数对系统性能的影响。研究结果表明，在平均压力为7MPa，加热温度为923K时，该系统能够获得1478W制冷量，相当于12．4％相对卡诺效率。本文对后续实验工作具有重要指导意义。

英文摘要：

Looped multi-stage thermacoustically driven cryocoolers are considered as promising candidates for applications in liquefaction and recondensation of natural gas. This paper introduces a new configuration capable of cascade power amplification, which could achieves kW-class cooling power and high thermal-to-cold efficiency at natural gas liquefaction temperature. Based on the classic thermoacoustic theory, a three-stage system is numerically investigated. Firstly, the axis distributions of the acoustic power are presented. Then, a comparison is made between this configuration and the previous multiple-coolers configuration The result shows that, this configuration not only has an advantage of structural simplicity and cooling easy-access, but also comparable to the previous configuration in system performance. In addition, emphasis is put on the influence of some key parameters such as area ratio of resonance tube, resonance tube length and heating temperature, which are found to be critical to the engine performance According to the calculation results, a cooling power of 1478 W and a global exergy efficiency of 12.4% is achieved with 923 K heating temperature and 7 MPa pressurized helium gas. This paper provides significant guidance for future experimental work.