35K两级高频脉管制冷研究:Ⅰ.理论分析

针对空间35K温区探测器的冷却需要,基于回热器数值计算软件REGEN3.2,成功设计了一台两级高频脉管制冷机.该制冷机采用热耦合的级间布置和惯性管调相方式,其中第二级脉管热端的惯性管和气库置于第一级脉管的冷头下,即冷惯性管,较好地解决了第二级脉管内小声功流条件下相位调节的难题.给出了第二级脉管制冷机的详细设计方法,讨论了第二级回热器填料、长度、充气压力对脉管制冷机性能的影响.计算表明,在80～35K,40Hz下,采用500目不锈钢丝网作为回热器时的制冷性能优于铅丸回热材料,充气压力在1.25MPa下可以获得较好的制冷性能.     

热声发动机驱动的脉管制冷机模拟及实验研究

基于回热器计算软件REGEN3.2,通过数值模拟分别研究了热声发动机的频率、输出压比、充气压力以及脉管制冷机的回热器长度对热声驱动的脉管制冷机制冷性能的影响,并预测了该台脉管制冷机的最低制冷温度为45K.实验研究了不同工质、热声发动机输出压比、声功输出装置以及脉管制冷机回热器长度对脉管制冷机性能的影响.实验结果表明,热声驱动的脉管制冷机的优化方向为提高热声发动机的输出压比、降低频率以及适当提高充气压力,这与数值模拟结果吻合较好.实验采用氮气-氦气双工质并以亥姆霍兹共鸣器作为声功输出装置和声压放大器,行波型热声发动机驱动的单级斯特林型脉管制冷机获得了65K的最低制冷温度.     

双向进气型脉管制冷机完整线性模型

基于完整线性模型分析了双向进气型脉管制冷机的制冷机理,并考虑了回热器空体积和气库压力波动的影响.假定回热器微元内的体积流量正比于局部压力梯度,通过代数方法建立了用于分析双向进气型脉管制冷机的完整线性模型.给出了制冷量、脉管冷端流量与压力相位差及性能系数与气库体积、工作频率、小孔与回热器流导系数之比及旁通阀与回热器流导系数之比的关系表达式.考察了工作频率、气库与脉管体积比对制冷机性能的影响,得到了与试验结果一致的最优工作频率.分析结果表明,冷端相位差随双向进气阀开度的增加而减小,从理论上证实了当工作频率约为1.4 Hz时制冷机产生最大制冷量,而当工作频率约为1.0 Hz时制冷机效率最高.     

35K两级高频脉管制冷研究：Ⅱ.实验验证

针对空间35K温区探测器的冷却需要,结合回热器数值计算软件REGEN3.2的计算分析,自行研制了一台第二级脉管采用低温惯性管和低温气库的热耦合型两级高频脉管制冷机.实验研究了充气压力、工作频率、输入功率等对第二级脉管制冷机性能的影响.实验得到35K下最佳充气压力为1.26MPa,最佳工作频率为40Hz,从而验证了理论计算结果.实验结果表明,在充气压力为1.26MPa,工作频率为45Hz,输入功率为135W的条件下,获得了27.4K的最低无负荷制冷温度;在充气压力为1.36MPa,工作频率为40Hz,输入功率为205W的条件下,制冷机在35K获得了0.45W的制冷量.     

新型热声发动机驱动的脉管制冷机实验研究

为完全消除低温系统中的运动部件,简化低温系统结构并提高其可靠性,对自制新型热声发动机驱动的脉管制冷机系统进行了实验研究.对热声发动机的性能进行了实验分析,确定出系统充气压力和制冷机的接口位置,将一台单级小孔型脉管制冷机接到系统中.通过调节小孔阀,对脉管制冷机性能进行了优化.结果表明,以氦气为工质,在充气压力为2MPa时,发动机单独运行时最大压比达1.19,驱动单级小孔型脉管制冷机获得了119K的低温,这为热声制冷机系统应用于天然气液化奠定了良好基础.     

针束型回热器熵产率的分析

回热器是热声装置的关键部件,在多种具有规则流道的回热器结构中,针束型结构是综合性能最优的结构.针对针束型回热器参数优化问题,建立了以最小熵产率为目标的优化模型,研究基于不可逆性的回热器参数优化方法.通过分析工质在回热器内振荡时由于与固壁的换热和黏性扩散导致的热动力学上不可逆性,对工质在针束型回热器内运动时的熵产率进行了理论分析和数值计算.计算获得了回热器截面分布和截面平均熵产率表达式,分析了针束型回热器中不同位置截面分布熵产率的变化规律,分析了温度梯度对截面平均熵产率的影响,获得了给定特征尺寸截面平均熵产率最小时的最优频率和最优阻抗比.     

不同填料对丝网回热器性能的影响

用不同粒径的铜丝网和不锈钢丝网为填料,分别制作了6种不同的回热器（标号为R1-R6）,通过实验对它们的性能进行了考察. 研究结果表明:丝网的材料、粒径和组合方式不同,对回热器性能的影响不尽相同. 通过比较不同回热器的回热损失及综合效率发现,单段式丝网回热器R1-R3的回热损失和综合效率各有优缺点,而采用适当组合后的多段式丝网回热器R6性能最优;当回热器热端选择粒径较小的丝网及在冷端采用导热率低的填料时,可大大提高回热器的换热效率.     

斯特林制冷机回热器间隙密封冷量损失分析(一)

回热器是斯特林制冷机冷头的重要组成部分。传统的回热器使用接触式滑动密封,存在磨损,限制制冷机的使用寿命。采用间隙密封,可以在完成密封作用的同时消除接触磨损和因此而产生的污染。但由于间隙内气体的泄漏,引起了冷量损失,使制冷量减少。建立了层流工况下斯特林制冷机回热器与气缸壁密封间隙泄漏率的数学物理模型,推导了密封间隙的泄漏率及泄漏引起的冷量损失的表达式。     

液氦温区双小孔型二级脉管制冷机实验研究

介绍了自行研制的二级双小孔型脉管制冷机的基本结构,着重分析了第二小孔、结构参数对制冷机性能的影响,指出了进一步改进的方向.反复实验表明,采用双小孔结构的二级脉管制冷机第一、第二级最低制冷温度分别达到46K和3.0K.     

斯特林制冷机回热器间隙密封冷量损失分析(一)

回热器是斯特林制冷机冷头的重要组成部分。传统的回热器使用接触式滑动密封，存在磨损，限制制冷机的使用寿命。采用问隙密封，可以在完成密封作用的同时消除接触磨损和因此而产生的污染。但由于间隙内气体的泄漏，引起了冷量损失，使制冷量减少。建立了层流工况下斯特林制冷机回热器与气缸壁密封间隙泄漏率的数学物理模型，推导了密封间隙的泄漏率及泄漏引起的冷量损失的表达式。     

The third type DC flow in pulse tube cryocooler

New phenomena discovered in the experimental research of the ultra-high frequency pulse tube cryocooler were presented. The cause of the new phenomena was analyzed and the third type DC flow was discovered in the pulse tube cryocooler. The third type DC flow not only deteriorated cooling capacity but also led to temperature instability of the pulse tube cryocooler. From the fluid network theory and the simple regenerator model, the root of the third type DC flow was concisely investigated in theory. The asymmetric resistance of oscillating flow in pulse tube cryocooler was the key mechanism of the third type DC flow. Some suppression methods were briefly discussed.     

A miniature liquid helium temperature JT cryocooler for space application

Along with the development of space science and technology,miniature liquid helium temperature long life cryocooler is a focus subject in cryogenic study.Since it is the precondition of space detection researches,institutions of space in many countries do the research on it.In this article,we designed a compound cooling system.A three-stage high frequency thermal coupled pulse tube cryocooler was used to precool a Joule-Thomson(JT)cryocooler.This system has no moving parts at low temperatures and is hence suitable for space operation.Liquid helium temperature was successfully achieved in both open loop and closed cycle experiments.In the closed cycle experiment,when 473 W electric power was inputted,the cooling system reached a no-load temperature of 4.4 K,and a cooling capacity of 11.6 mW was provided at 4.54 K.It is the first miniature liquid helium temperature JT cryocooler in China and the research achievement paves a way for the space application of ultra-long wave infrared detection and THz technologies.     

Attaining the liquid helium temperature with a compact pulse tube cryocooler for space applications

Recent breakthroughs in space science have motivated space exploration programs in many countries including China. Cryocoolers, which provide the mandatory low-temperature environment for many sensitive yet delicate space detectors, are crucial for the proper functioning of various systems. One benchmark for the cryocooler performance is attaining the liquid helium temperature. However, even with complex configurations and multiple driving sources, only a few cryocoolers to date can achieve this goal. Here we report a high-frequency pulse tube cryocooler(HPTC) driven by a single non-oil-lubrication compressor which is capable of reaching the liquid helium temperature while offering other advantages such as high compactness, excellent reliability and high efficiency. The HPTC obtains a no-load temperature of 4.4 K, which is the first realization of cooling below the4 He critical point with a gas-coupled two-stage arrangement. The prototype can provide a cooling power of 87 mW at 8 K, and 5.2 mW at 5 K with a 425 W input electric power, showing leading-level efficiency. Moreover, we demonstrate the ability of the cryocooler to simultaneously provide cooling power at different temperature levels to meet different requirements. Therefore, the prototype developed here could be a promising cryocooler for space applications and beyond.     

Advance in research of several types of streaming of pulse tube refrigerators

The pulse tube refrigerator(PTR)is a promising small-scale cryocooler.This paper first briefly introduces the history of the pulse tube refrigerator.It has pointed out that technology improvements and theoretical developments of the pulse tube refrigerator closely relate with the internal streaming effects.Then the discovering history and classification of the streaming or DC(direct current)flow effect are summarized.It proposes for the first time that the physical significance of the streaming contains the driving mechanisms and the transport mechanisms.It demonstrates that the driving mechanisms are the asymmetry of fluid flow and temperature while the transport mechanisms are a loop or vorticity,which transmits nonlinear dissipations.The important advancements have been made over the past two decades all over the world in research of streaming of the pulse tube refrigerator including Gedeon DC flow,Rayleigh streaming,the third type of DC flow and the regenerator circulation.With regard to Gedeon DC flow,theoretical and experimental analyses have been made and different suppression methods are summarized.In the aspect of Rayleigh streaming,it mainly focuses on the analytical solution of the second-order mass flow and the research of tapered pulse tubes.In particular,limited research on the third type of DC flow and regenerator circulation is presented.The experimental measurement techniques of streaming also are summarized.Finally,this paper briefly discusses the key scientific and technical issues of the current research,and foretells the future development trends of streaming research in PTR.     

磁共振成像低温超导磁体冷却系统设计及数值分析

为了减小冷却磁共振成像（MRI）低温超导磁体的资源消耗和经济成本,设计可快速冷却室温磁体至60 K以下的系统,并通过建立数学物理模型进行数值模拟,对系统进行优化设计和深入分析. 系统以自主研发的大冷量单级斯特林制冷机为冷源,包括低温风机、低温调控阀和氦气罐等组成部分. 研究表明,优化系统运行参数可以显著提高冷却性能,其中系统内氦气的压力和流速尤为关键,因为两者能够显著影响压降与换热,进而影响冷却时间以及磁体最终所能达到的冷却温度. 此外,当前斯特林制冷机的冷端换热器性能尚有提升空间. 通过参数优化,系统在氦气压力为0.3 MPa、流速为13 m/s时能够达到较快的冷却速率,可在73.5 h内将质量为2 t的室温超导磁体冷却至60 K以下,有潜力在实际应用中实现MRI低温超导磁体的低能耗高效冷却.     

镇海炼油厂RFCC装置第一再生器的冷模实验研究

本文为了考察镇海炼油厂RPCC装置第一再生器的操作状况,根据几何相似原理建立了冷模实验装置,并采用示踪剂脉冲响应技术,测定了不同实验条件下催化剂在流化床再生器中的停留时间分布,对影响再生器操作的主要因素进行了分析研究,从而提出了改进第一再生器操作的具体措施。     

二级塑料斯特林制冷机的热力设计探讨

本文对二级塑料斯特林制冷机的传热和流体流动进行了分析,以第二级最低制冷温度为目标函数,进行了二级机的直径比和长度比的优化设计探讨,给出了直径比和长度比与各级制冷温度和理论功耗的三维函数图,指出了转速、冲程和缝隙尺寸对塑料制冷机制冷性能的影响。