The use of closed cycle coolers on space based observatories

Many proposed space based observations will rely on the use of closed cycle and passive cooling systems to provide the thermal environment for high sensitivity. The use of closed cycle mechanical coolers on space telescopes poses particular integration problems; some of these difficulties are discussed in this paper.One of the major problems envisaged is that of exported vibration. This problem, and that of the heat sinking required, can be alleviated by siting the compressors of the Stirling cycle precooler further from the displacer unit. The effect of the separation between the compressors and the displacer on the performance of the Stirling cycle precooler has been measured. Increasing the separation from 170 mm to 565 mm decreases the cooling power at 25 K from 220 mW to 180 mW. In most applications this would be acceptable.The pre-cooler provides cooling at a single point. In situations where refrigeration of extended objects (e.g. telescope mirrors) is required, some distribution method has to be found. A scheme for achieving this is presented together with preliminary calculations on such a system.Temperatures in the region of 2.5 to 4K are required to meet the requirements for long wavelength detectors. We have demonstrated how these temperatures can be achieved in a continuously operating closed cycle cooler that has been engineered for space applications. This cooler consists of a two-stage Stirling cycle precooling a closed cycle Joule-Thomson (JT) stage. Temperatures in the region of 4K are achieved by the use of helium-4 in the JT system. The lighter isotope of helium is used to obtain temperatures down to 2.5 K. Under no-load conditions the precooler reaches a base temperature of 11.3K. The JT system achieves 4.3 K with a 10 mW heat load and 2.5 K with a heat load of over 3 mW. The input power to the cooler is approximately 126 W.The temperature stability of the cooler at low temperatures is important to keep detector drift to a minimum. The temperature of the JT stage has been measured in uncontrolled laboratory conditions and found to vary by only 30 mK over a seventy hour period. The pre-cooler temperature varied by approximately 0.6 K during these measurements.     

Closed cycle coolers for space applications

Single stage Stirling coolers providing refrigeration at around 80 K have been developed for space use and are now being produced commercially. Development work is now concentrating on multistage coolers for temperatures below 30 K. This paper describes results from a two stage cooler built at the Rutherford Appleton Laboratory and preliminary tests on a closed cycle 4 K cooler.     

空间微小脉冲管制冷机研制

随着空间机械制冷技术的迅速发展,空间脉冲管制冷机在80 K温区整机效率已经优于1 W/18 W（制冷量/输入电功）。针对中国航天未来微小卫星的发展,中国科学院理化技术研究所开展了空间微小脉冲管制冷机的研究,并获得突破性的进展。理化技术研究所研制的宇航级微型脉冲管制冷机,80 K温区制冷量与重量比已经大于1.5 W/1 kg,制冷效率达到1 W/22.5 W（制冷量/输入电功）,在轨设计寿命超过30 000 h,可以与中波红外320×256以下面阵探测器直接耦合。系统介绍了中国科学院理化技术研究所微型脉冲管制冷机的研发过程,并给出了最新的研发结果。该制冷机除了可以实现给中波红外探测器制冷以外,还可以作为辅助热控手段,对220 K以下温区的载荷热控、载荷在轨气体多余污染物吸附等应用提供帮助。     

节流制冷对低温贮箱主流液体控温影响分析

为研究低温流体节流特性及冷量引入对贮箱主流体控温影响,首先对低温流体节流干度和体积含气率进行了分析,结果表明质量占比较小的气相占据了大部分空间体积,对流动速率及换热产生较大影响;建立了节流制冷性能测试平台,采用液氮工质开展了节流前压力为0.3～0.37 MPa工况下的减压降温试验,节流前后降温达到了11.3～14.2 K;在集成节流阀孔的热力学排气系统（TVS）系统中,通过节流制冷使贮箱流体产生了平均6.5 K的温降,将贮箱压力控制在150～160 kPa范围;冷量的引入使主流区液体温度持续波浪式降低,气液界面热分层处的降温效果更加明显。     

液体火箭发动机推力室再生冷却流动与传热计算研究

为了研究液体火箭发动机推力室再生冷却流动与传热的快速仿真方法,建立了推力室再生冷却的准二维模型,对航天飞机主发动机开展了再生冷却流动与传热计算仿真研究,对比分析了再生冷却准二维模型和三维模型的仿真计算结果。研究表明,两种计算模型均可较好地预测推力室燃气及再生冷却剂的流动和传热。三维模型计算精度高,但计算用时较长。计算得到的航天飞机主发动机的燃气侧壁面最高热流密度为162.2MW/m2,最高壁温为1159.7K,冷却剂温升为244.0K,压降为8.5MPa。准二维模型计算结果精度略有降低,但计算时间较三维模型减小了90%。四个参数与三维模型计算结果的差异分别为0.3%,4.4%,8.6%和4.5%,在可接受范围内。本文的准二维模型计算时间短,适用于液体火箭发动机再生冷却结构的方案筛选和优化设计,三维模型计算精度高,适用于设计完成后的校核计算。     

AFRL Cryogenic Technology Development Programs

This is an overview of the cryogenic refrigerator and cryogenic integration programs in development and characterization under the Cryogenic Technologies Group, Space Vehicles Directorate of the Air Force Research Laboratory (AFRL). The vision statement for the Air Force Research Laboratory Cryogenic Technologies Group is to support the space community as the center of excellence for developing and transitioning space cryogenic thermal management technologies. The primary customers for the AFRL cryogenic technology development programs are Ballistic Missile Defense Organization (BMDO), the USAF SBIRS (space based infrared) Low program office, and DoD space surveillance programs. This describes a variety of Stirling, pulse tube, Reverse Brayton, Joule-Thomson, and Sorption cycle cryocoolers currently under development to meet current and future Air Force and DoD requirements. The AFRL customer single stage cooling requirements at 10 K, 35 K, 60 K, 150 K, and multi-stage cooling requirements at 35/60 K are addressed. In order to meet these various requirements, the AFRL Cryogenic Technologies Group is pursuing various strategic cryocooler and cryogenic integration options. The Air Force Research Laboratory is also developing several advanced cryogenic integration technologies that will result in the reduction in current cryogenic system integration penalties and design time. These technologies include the continued development of the cryogenic systems integration model (CSIM), 60 K, and 100 K thermal storage units and heat pipes, cryogenic straps, thermal switches, and development of an integrated lightweight cryogenic bus (CRYOBUS).     

基于半导体制冷高效热回收装置的研究

从笔记本电脑散热难的问题出发,初步设计了以半导体制冷技术为基础,利用热端回收装置有效解决笔记本电脑散热问题。通过在实际应用中进行测试和试运行,实践证明该系统设计的合理性和可行性。而且通过该热回收装置有效提高了半导体制冷效率及热量的高效利用。在此基础上融合了负离子空气清新技术,利用负离子的良好功能,给上网者提供了良好健康环境。并为解决小型设备散热提出了新的思路。     

基于G-M制冷机的大尺寸冷屏设计方法

介绍了基于Gifford-Mcmahon (G-M)制冷机的大尺寸冷屏的设计方法。该低温冷屏配合真空环境模拟室共同使用,为遥感卫星的星载遥感器等部件的红外定标试验提供20K的低温冷背景。该冷屏采用5台G-M制冷机进行制冷,外形尺寸达到1m×1m,是目前国内同类型冷屏中尺寸最大的。详细介绍了冷屏在容器内的安装布置、冷缩时的补偿等结构设计方法、冷屏的表面温度分布以及降温时间等计算分析。成功解决了大尺寸冷屏在低温环境下的冷缩补偿难题,试验结果表明:冷屏主要测点温度为15K,温度均匀性误差为±1K,达到并超过设计要求。      

蒸汽压缩式制冷系统在航空中的应用

通过对空气压缩式、蒸汽压缩式、热电制冷3种制冷系统的比较,提出蒸汽压缩式制冷系统是最适合应用于制冷量需求较大的航空电子设备,并着重介绍了蒸汽压缩式制冷系统的工作原理、关键技术及其优越性。     

基于TEC的空间站末端回路温控系统建模及其热力学性能分析

针对空间站中间回路温度波动过大,高温时导致科学载荷工作温度超出允许范围的问题,设计了一种基于热电制冷器(TEC)的末端单向流体回路温控系统。该系统包含一个TEC温控模块,当中间回路温度过高,末端回路冷却功率不足时,该模块可提供额外的制冷量,降低流入冷板的工质温度,形成针对科学载荷的相对低温区域,恢复回路的冷却能力。分别建立了温控系统数学模型与数值仿真模型,并完成了热负载扰动、中间回路温度扰动、末端回路流量扰动和并联支路热扰动等4种扰动对系统热力学特性影响的仿真分析,验证了TEC模块的温控性能。结果表明:在科学载荷发热功率增加30%、中间回路的温度升高5K、末端回路流量减小至0.0015kg/s等多种工况下,所设计的温控系统能够将载荷温度控制在1K以内,实现科学载荷精确温控。      

飞机燃油箱冷却惰化系统地面性能分析

设计了冷却惰化系统的工作流程并建立了地面状态下冷却惰化的数学模型,通过Modelica软件求解得到了油箱气相空间燃油蒸汽体积分数,燃油和气相空间温度以及制冷量随时间变化关系,并且研究了几个关键参数对惰化效果的影响。结果表明:随着抽气流量的增加和蒸发温度的降低,气相空间燃油蒸汽体积分数越低,气相空间温度也越低,达到冷却惰化的时间也越短,惰化效果也越好。虽然内热源对冷却惰化的效果起到了阻碍的作用,内热源越大,冷却惰化越难实现。但整体上看,冷却惰化是油箱惰化的一种可行替代方法。      

Multi-parameter decoupling and slope tracking control strategy of a large-scale high altitude environment simulation test cabin

A large-scale high altitude environment simulation test cabin was developed to accurately control temperatures and pressures encountered at high altitudes. The system was developed to provide slope-tracking dynamic control of the temperature–pressure two-parameter and overcome the control difficulties inherent to a large inertia lag link with a complex control system which is composed of turbine refrigeration device, vacuum device and liquid nitrogen cooling device. The system includes multi-parameter decoupling of the cabin itself to avoid equipment damage of air refrigeration turbine caused by improper operation. Based on analysis of the dynamic characteristics and modeling for variations in temperature, pressure and rotation speed, an intelligent controller was implemented that includes decoupling and fuzzy arithmetic combined with an expert PID controller to control test parameters by decoupling and slope tracking control strategy. The control system employed centralized management in an open industrial ethernet architecture with an industrial computer at the core. The simulation and field debugging and running results show that this method can solve the problems of a poor anti-interference performance typical for a conventional PID and overshooting that can readily damage equipment. The steady-state characteristics meet the system requirements.     

超声速飞行器综合热管理系统优化设计

针对飞行器超声速巡航时遭受机体外部气动加热与辐射换热的情况，提出了一套综合考虑燃油系统、冲压空气与消耗性冷却剂制冷系统及热防护系统的超声速飞行器综合热管理系统；针对典型的超声速飞行包线，基于二阶多项式响应面代理模型技术，以热防护层厚度、回油质量流量以及消耗性相变冷却剂质量流量为设计变量，以燃烧室进口燃油温度为约束条件，以变量引起的起飞重量增量及其燃油质量代偿损失最小为设计目标，采用自适应模拟退火算法对综合热管理系统进行了优化设计。结果表明：采用二阶多项式响应面代理模型计算的结果与仿真计算结果的误差低于2%；在本文选取的设计变量取值范围内，最优方案倾向于热防护层厚度和冷却剂质量流量取最小值而回油质量流量取中间值，且最优方案较第一组初始方案就目标函数而言减重约16%。     

空空导弹固体火箭冲压发动机设计参数优化

为使空空导弹在较宽的空域范围内获得优化的综合性能,提出了以导弹综合特性为目标函数来优化固体火箭冲压发动机设计参数的思路,以空空导弹在飞行高度分别为5,10km和15km的飞行距离和飞行速度的综合性能参数为目标函数,建立了固体火箭冲压发动机设计参数优化模型,利用遗传算法进行了固体火箭冲压发动机设计参数的优化.优化的结果表明:当参数选择适当时,采用非壅塞固体火箭冲压发动机的空空导弹在较宽的工作包线内也能够具有优秀的飞行性能,在高度为5,10km和15km时,空空导弹的飞行距离分别达到了62.9,89.2km和133.1km,空空导弹的平均飞行速度也得到了提高.      

Optimised radiative cooling of infrared space telescopes and applications to possible missions

General principles are outlined for the design of space infrared telescopes intended to cool by radiation to the lowest temperatures attainable without the use of on-board cryogens, and assuming on-orbit cooling after a warm launch. Maximum protection from solar and earth heating, maximum radiating area and efficiency and minimum absorbing area and absorptivity are the obvious basic criteria. The optimised design is a short, fat telescope surrounded by a series of radiation shields, each cooled by its own radiator. Maximising the longitudinal conductivity of the radiation shields and of the telescope tube itself is important both to the on-orbit cooling time and the final achieveable temperature. Realistic designs take between 80 and 200 days to cool to within a few degrees of equilibrium temperatures, depending on the materials used. Great advantages accrue from the use of an orbit distant from earth. Both simple models and detailed simulations suggest that temperatures of 30 to 40 K are attainable in high earth orbits. Placing a radiatively cooled telescope in a halo orbit around the Lagrangian point L2 is a particularly attractive option and significantly lower temperatures can be achieved there than in Earth orbit. Optimised radiative cooling is an important element of the small Japanese mission SMIRT. We suggest that a combination of an ESA Medium-sized Mission with a NASA Explorer to send a 2m+ telescope to an L2 halo orbit would provide a cost-effective and powerful long-duration facility for the early 21st century.     

Radiative and hybrid cooling of infrared space telescopes

The designs of cold space telescopes, cryogenic and radiatively cooled, are similar in most elements and both benefit from orbits distant from the Earth. In particular such orbits allow the anti-sunward side of radiatively-cooled spacecraft to be used to provide large cooling radiators for the individual radiation shields. Designs incorporating these features have predictedT _tel near 20 K. The attainability of such temperatures is supported by limited practical experience (IRAS, COBE). Supplementary cooling systems (cryogens, mechanical coolers) can be advantageously combined with radiative cooling in hybrid designs to provide robustness against deterioration and yet lower temperatures for detectors, instruments, and even the whole telescope. The possibility of such major additional gains is illustrated by the Very Cold Telescope option under study forEdison, which should offerT _tel5 K for a little extra mechanical cooling capacity.     

基于启发强化学习的大规模ADR任务优化方法

随着航天事业的蓬勃发展,空间碎片尤其是低轨碎片已成为航天任务不可忽视的威胁。考虑到碎片清除的紧迫性和成本,低轨多碎片主动清除（ADR）技术成为缓解现状的必要手段。针对大规模多碎片主动清除任务规划问题,首先,基于任务规划的最大收益模型,提出一种强化学习（RL）优化方法,并依照强化学习框架定义了该问题的状态、动作以及收益函数;其次,基于高效启发因子,提出一种专用的改进蒙特卡罗树搜索（MCTS）算法,该算法使用MCTS算法作为内核,加入高效启发算子以及强化学习迭代过程;最后,在铱星33碎片云的全数据集中检验了所提算法有效性。与相关MCTS变体方法以及贪婪启发算法对比,所提方法能在测试数据集上更高效地获得较优规划结果,较好地平衡了探索与利用。     

Optimization on conventional and electric air-cycle refrigeration systems of aircraft: A short-cut method and analysis

The air-cycle refrigeration system is widely used in commercial and military aircraft, and its efficiency greatly affects aircraft performance. Nowadays, this system requires a more efficient design and optimization method. In this paper, a short-cut optimization method with high efficiency and effectiveness is introduced for both conventional and electric air-cycle refrigeration systems. Based on the system characteristics, a four-layer parameter matching algorithm is designed which avoids computational difficulty caused by simultaneous equations. Fuel penalty is chosen as the objective function of optimization; design variables are reduced based on sensitivity analysis to improve optimization efficiency. The results show that the 3-variable optimization of the conventional air-cycle refrigeration system can obtain almost the same results as the traditional 6-variable optimization in that these two optimizations can both significantly reduce the fuel penalty. However, the computer running time of the 3-variable optimization is much shorter than that of the 6-variable optimization. The optimal fuel penalty of the electric air-cycle refrigeration system is lower than that of the conventional one. This study can provide reference for optimizing the air-cycle refrigeration system of aircraft.     

不同结构的冷却管脉冲射流流动响应特性

探究了结构参数对脉冲射流经冷却管内流动响应规律.在脉冲频率为1Hz,雷诺数为5000,脉冲射流占空比为50％的气动参数下,对冷却管管径、射流孔孔径、孔间距的变化对脉冲射流流动响应特性带来的影响依次分析,对结构参数对脉冲射流在冷却管内流动响应特性产生影响的内在机制进行综合阐述.针对上述结构参数拟合出冷却管射流质量系数随冷...     

GH4096合金固溶冷却方式对性能和残余应力的影响

为了在保证GH4096合金主要力学性能的前提下,降低薄壁类零件用锻件的内部残余应力,提高零件加工过程的尺寸控制精度,研究空冷,风冷,油冷,盐浴等固溶冷却方式对GH4096合金环锻件析出相的尺寸和形貌、主要力学性能和内部残余应力的影响。结果表明:与采用传统油冷的试件相比,空冷试件的二次、三次γ′相较为粗大,蠕变性能和高温拉伸性能有较大幅度的降低,风冷试件的二次γ′相尺寸略有增大,三次γ′相尺寸相当,蠕变性能和拉伸性能有小幅降低,盐浴冷却试件的二次、三次γ′相尺寸相当,蠕变性能和拉伸性能相差较小。采用风冷的试件内部残余应力可控制在±100 MPa以内,比油冷和盐浴冷却的试件降低50%以上。GH4096合金环件固溶处理冷却方式采用风冷与传统的油冷和盐浴冷却方法相比,可以明显降低锻件内部残余应力,蠕变和高温拉伸等性能只有小幅降低,有助于改善GH4096合金薄壁零件冷加工过程的变形问题,提高尺寸控制精度。