液氦温区斯特林型脉管制冷机回热强化机理研究

液氦温区高效、紧凑、长寿命的低温制冷技术是国防、航天、超导、医疗等领域的重要支撑和保障。液氦温区的斯特林脉管制冷机因其具有体积小、振动低等优势，成为低温制冷领域的研究热点。然而深低温下高频运行造成回热损失严重，导致当前斯特林脉管制冷机难以实现液氦温区高效制冷。本项目以显著提高液氦温区斯特林脉管制冷机效率为目标，提出利用基于频率特性的多参数耦合优化方法以及低温传输管声功驱动方式，显著降低回热器换热和阻力损失。探索液氦温区运行频率、压比、不同填料组合对回热器各损失的影响机理，揭示液氦温区回热器的最佳运行工况；提出新的声功测算方法对整机功损进行评估，分析低温传输管的声阻抗特性，探索制冷机与压缩机的高效匹配方式；研制基于最佳设计工况的低温声功驱动型斯特林脉管制冷机，最终实现液氦温区的高效制冷。

The high-efficiency, compact and long-life cryocoolers working at liquid helium temperatures play a crucial role in national defense, space application, superconductor, and medical usages. Recently, the Stirling pulse tube cryocooler (PTC) has become a hot topic in the worldwide cryocooler research field due to its compactness, low vibration and other advantages. However, it is still hard for the Stirling PTC to work efficiently around 4.2 K owing to its severe regenerator losses under high-frequency operation. This project aims to increase the refrigeration efficiency of Stirling PTC through enhancing its regenerator performance and decreasing its consumed power at liquid helium temperatures. A multiple-parameter coupling method based on frequency has been proposed to optimize the regenerator. The effect of different frequencies, pressure ratios, and regenerative material combinations on the regenerator losses will be explored to reveal the optimum operating conditions for the regenerator under liquid helium temperatures. An approach of driving acoustic power through a cold transmission tube is also proposed in order to eliminate the pressure loss in the regenerator at higher temperatures. By utilizing a new acoustic power measurement, the acoustic loss of the cryocooler and the impedance characteristic of the cold transmission tube will be estimated and analyzed, exploring the perfect matching between the cryocooler and the linear compressor. A Stirling PTC based on the above optimizations will be built and tested to realize high-efficiency refrigeration at liquid helium temperature in experiment. This study is benefit to the development of regenerative cryocoolers, and is also of great significance to the development of recent cryogenic application fields.