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.     

民用飞机预冷器设计点选取方法研究

预冷器是民用飞机气源系统温度调节的重要部件,若发生超温将导致系统自动关闭,影响下游机翼防冰系统和空调等系统用气需求,对飞机安全性有重要影响,因此研究预冷器设计点满足温度调节需求对气源系统设计有着重要意义。首先分析了预冷器换热性能影响关系,进而对其性能影响因素进行分析,主要包括环境条件信息,飞机状态信息,气源系统引气构型。然后根据经验公式对某机型不同工况条件下预冷器换热功率因子进行计算。计算结果表明在严酷引气构型双发单引气条件下,极热天巡航或待机状态下,低高度、低马赫数、低重量条件为预冷器设计点。通过计算严酷工况下预冷器热边出口温度,对预冷器设计点进行校核,计算结果表明预冷器热边出口温度均满足预冷器预期温度,说明预冷器设计点选取满足设计需求。     

Microstructural evolution and mechanical properties of brazed IN718 ultrathin-walled capillary structure using different particulate reinforced filler alloy

The development of hypersonic precooled combined cycle engine provides a reliable power system for the future intercontinental navigation and reusable space orbital transportation.The compact heat exchanger precooler is the key component of the cooling cycle system, which provides efficient heat management for the hypersonic engine. This investigation mainly focused on the manufacturing process of precooler, and the typical structure of the precooler, ultrathin-walled capillary structure, was fa...     

SABRE预冷器计算模型及其在整机模型中的应用

预冷器的性能对SABRE等预冷组合循环发动机具有重要影响,为实现发动机方案设计阶段预冷器的快速设计与评估,建立了预冷器准二维快速评估模型。将SABRE预冷器的几何结构简化为一个扇环形区域,沿径向和周向将该区域划分为二维节点。应用守恒方程及传热关联式完成单个节点计算,再求解节点矩阵的平衡方程组,计算内外流体特定节点上参数的二维分布,得到预冷器出口参数。将模型嵌入发动机总体性能程序中,实现了发动机设计及非设计点的预冷器性能计算的功能。与文献数据对比结果表明,预冷器模型传热计算误差小于5%,摩擦阻力误差小于10%。整机计算结果显示,Ma0~5范围内,预冷器空气侧温降范围为143K至932K,温降随飞行马赫数升高单调上升。预冷器传热有效度范围为0.896-0.945,空气侧总压恢复系数范围为0.852-0.904。     

临近空间飞行器推进系统预冷器关键技术

临近空间由于其在现代战争中的重要战略意义已成为各国航空航天领域的研究重点,高超声速飞行器更是国家临近空间军事实力的一个重要标志。由于吸气式高超声速飞行器具有较高的飞行高度与马赫数,预冷技术已成为高超声速飞行器推进系统中的一项关键技术,而高性能预冷器设计是预冷技术的一个重要研究方向,预冷器的可靠性与流动传热特性是预冷系统的重要影响参数,对于紧凑、高效、高可靠性先进预冷器的研究具有十分重要的意义。基于目前公开的临近空间高超声速飞行器的主要动力形式及其对预冷技术的刚性需求,对预冷器设计中的关键技术与发展方向做了详细的阐述。     

Adiabatic demagnetisation refrigerators for future sub-millimetre space missions

Space worthy refrigeration capable of providing a 100 mK and below heat load sink for bolometric detectors will be required for the next generation of sub-millimetre space missions. Adiabatic demagnetisation refrigeration (ADR), being a gravity independent laboratory method for obtaining such temperatures, is a favourable technique for utilisation in space.We show that by considering a 3 salt pill refrigerator rather than the classic single salt pill design the space prohibitive laboratory ADR properties of high magnetic field (6 Tesla) and a<2 K environment (provided by a bath of liquid⁴He) can be alleviated, while maintaining a sufficient low temperature hold time and short recycle time. The additional salt pills, composed of Gadolinium Gallium Garnet (GGG) provide intermediate cooling stages, enabling operation from a 4 K environment provided by a single 4 K mechanical cooler, thereby providing consumable free operation. Such ADRs could operate with fields as low as 1 Tesla allowing the use of high temperature, mechanically cooled superconducting magnets and so effectively remove the risk of quenching.We discuss the possibility of increasing the hold time from 3 hours, for the model presented, to between 40 and 80 hours, plus reducing the number of salt pills to two, through the use of a more efficient Garnet.We believe the technical advances necessitated by the envisaged ADRs are minimal and conclude that such ADRs offer a long orbital life time, consumable free, high efficiency means of milli-Kelvin cooling, requiring relatively little laboratory development.     

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。     

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。     

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).     

无水甲醇质量比对紧凑型预冷器的结霜和抑霜性能的影响

在主流来流的速度值、湿度值和温度值分别为10 m/s、6.4 g/kg和50℃的实验条件下，对微管式紧凑型预冷器的结霜和抑霜性能进行了实验研究。在抑霜实验工况中，采用无水甲醇作为抑霜的有机溶剂，且在抑霜实验过程中喷射了三个不同质量比（0.75、1.0和1.25）的无水甲醇对预冷器进行抑霜。对不同实验工况的结霜和抑霜性能、压力损失系数、预冷器管束的壁面温度和预冷器的换热率进行了详细地分析。实验结果表明，在进行结霜实验时，当低温冷却剂流经预冷器的微细管束内部时，在预冷器的外侧会快速地凝结霜层，且霜层随着实验时间的增长而逐渐累积。然而，一旦向主流来流中喷射了三个不同质量比的无水甲醇之后，会产生非常明显的抑霜效果，主流的压力损失系数显著下降且预冷器的换热率明显提高。此外，预冷器微细管束的壁面温度也显著的增大了，其壁面温度均高于水的冰点，这是喷射无水甲醇能够产生抑霜效果的直接原因。在向主流喷射三个不同质量比的无水甲醇的抑霜实验中，当喷射的无水甲醇的质量比为1.0时的抑霜效果最佳。此外，根据对抑霜实验结果进行分析，可以进一步地推测：实现最优抑霜性能的最佳无水甲醇质量比可能介于1.0～1.25之间。     

预冷组合循环发动机吸气式模态建模与性能分析

为了对预冷组合循环发动机开展性能分析，以协同吸气式火箭发动机（SABRE 4）为研究对象，采用部件法建立了发动机稳态模型，计算获得了SABRE 4发动机在吸气式模态下沿飞行弹道的性能参数变化规律。然后对发动机的高度和速度特性进行研究，得到了发动机的飞行包线。计算结果表明，在吸气式飞行弹道内，核心机推力和比冲的变化分别为488~680kN和34786~46954m/s。SABRE 4发动机具备推力大和比冲高的性能优势。在预冷器工作过程中，随着飞行马赫数增大，预冷器换热量不断增大，进入预燃室的氢流量减小，预燃室总温降低，HX3的吸热量减小。与其他压气机和涡轮相比，空气压气机和氦涡轮的工作参数变化较大。SABRE 4发动机通过对来流空气进行预冷，可实现在大空域和宽速域内工作。由于空气压气机的喘振和堵塞边界限制，发动机的高度和速度特性分别存在飞行高度和飞行马赫数的限制。     

Applications of Brayton cycle technology to space power

The Closed Brayton Cycle (CBC) power conversion cycle can be used with a wide range of heat sources for space power applications. These heat sources include solar concentrator, radioisotope, and reactor. With a solar concentrator, a solar dynamic ground demonstration test using existing Brayton components is being assembled for testing at NASA Lewis Research Center (LeRC). This 2-kWe system has a turbine inlet temperature of 1015 K and is a complete end-to-end simulation of the Space Station Freedom solar dynamic design. With a radioisotope heat source, a 1-kWe Dynamic Isotope Power System (DIPS) is under development using an existing turboalternator compressor (TAC) for testing at the same NASA-LeRC facility. This DIPS unit is being developed as a replacement to Radioisotopic Thermoelectric Generators (RTGs) to conserve the Pu-238 supply for interplanetary exploration. With a reactor heat source, many studies have been performed coupling the SP-100 reactor with a Brayton power conversion cycle. Applications for this reactor/CBC system include global communications satellites and electric propulsion for interplanetary exploration. applications. The CBC consists of a heater, turboalternator compressor (TAC), cooler, and recuperator. A mixture of He and Xe is used as the working fluid in the CBC system. The He provides superior heat transfer characteristics in the heater, cooler, and recuperator. The Xe adjusts the molecular weight to provide superior aerodynamic performance for maximized turbine and compressor efficiency. Cycle studies are performed to select the optimum He/Xe molecular weight or He to Xe mixture ratio. The following presents the characteristics and advantages of using the CBC for space power applications, CBC development status, characteristics and applications of the CBC with each of the heat sources, and finally performance projections     

气冷涡轮叶片三维换热问题计算

建立了三维气冷涡轮叶片换热计算的热-流耦合计算模型, 将辐射热量作为源项加入到方程中, 采用热-流耦合方法完成了某气冷涡轮叶片带辐射的三维换热计算.辐射热量的计算采用了P-1辐射模型, 比较了计算辐射和不计辐射时叶片表面的温度值及温度分布的差异.计算表明对于1600 K这样的高温燃气, 辐射热量不可忽略, 考虑辐射热量后, 叶片温度明显升高, 温度分布也产生了显著差异.      

预冷空气涡轮火箭发动机氦循环系统的参数特性

针对预冷空气涡轮火箭发动机(PATR)方案,建立氦循环系统数学模型,模型考虑组件结构特征、几何尺寸、工质物性等主要因素。数值计算表明:PATR的推力和比冲性能较优,模型可描述发动机氦循环热力过程,其中发动机余气系数是影响发动机推力、比冲的关键参数。提高氦循环系统最高设计压力和降低空气预冷器氦进口温度可有效降低压力损失和氦压气机功率,最高压力每增大1MPa,系统平均压力损失下降1.1%,氦压气机输入功率下降3.2%;空气预冷器氦进口温度每升高1K,系统平均压力损失上升0.086%,氦压气机输入功率升高2.3%。     

A refined design method for precoolers with consideration of multi-parameter variations based on low-dimensional analysis

The precooler is a distinctive component of precooled air-breathing engines but constitutes a challenge to conventional thermal design methods. The latter are based upon assumptions that often reveal to be limited for precooler design. In this paper, a refined design method considering the variations of fluid thermophysical properties, flow area and thermal parameters distortion,was proposed to remediate their limitations. Firstly, the precooler was discretized into a fixed number of sub-microtu...     

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。      

换热预冷发动机预冷特性和发动机性能数值研究

为深入了解换热预冷发动机换热器预冷效果和发动机性能,首先设计了叉排管束式细小通道换热预冷器,并采用非定常数值模拟方法对换热效果进行了仿真,然后结合换热预冷发动机性能计算程序对预冷发动机性能进行了研究。结果表明,飞行马赫数为2.5~4.0且氢气空气质量流比为0.03~0.09条件下,换热预冷器能将来流空气预冷90.6~471.2 K,低温氢气经吸热后温度升幅为266.1~455.3 K,换热效果良好。来流空气经预冷后涡轮发动机的飞行包线最高被拓展至马赫数4.0,达到了与超燃冲压发动机的衔接速域。相比于传统涡轮发动机,氢气空气质量流比为0.03时,本文换热预冷发动机加力状态推力能恢复至设计点推力水平;当氢气空气质量流比增加至0.09时,加力状态推力最高达到设计点推力的两倍左右。马赫数2.6以下换热预冷措施能小幅改善发动机比冲和耗油率（仅计算用于燃烧的氢气量）性能,而飞行速度大于马赫数2.6后换热预冷措施也难以抑制比冲和耗油率迅速恶化的趋势。     

液体火箭发动机推力室复合冷却流动与传热研究

为了预测液体火箭发动机推力室的复合冷却性能,建立了推力室再生冷却通道和超临界氢的三维仿真模型以及推力室内燃气和超临界氢膜的轴对称二维仿真模型。通过边界耦合发展了液体火箭发动机推力室复合冷却流动与传热的数值仿真方法。对航天飞机主发动机推力室内部燃气、超临界冷却膜、室壁和再生冷却剂进行了流动与传热耦合计算仿真研究。研究表明,仿真方法可较好地预测推力室燃气及再生冷却剂的流动和传热,计算得到航天飞机主发动机的燃气侧壁面最高热流密度为129MW/m2,最高壁温为885K,冷却剂温升为192K,压降为8.8MPa,结果与已有数据吻合较好。模型和仿真方法可用于液体火箭发动机推力室冷却系统传热计算和冷却结构的优化设计。     

超临界压力下航空煤油流动与传热特性试验

本文针对超燃冲压发动机再生冷却系统运行条件,实验研究了大庆RP-3煤油在超临界压力下的流动和传热特性,目的在于研究煤油在各种工况下的流动参数变化以及对流传热规律。煤油通过二级煤油加热/输运系统加热,试验的煤油压力约2.6M～5.0MPa,油温约300～800K。相应的壁面热流密度为10～300kW/m2。通过油温与壁温的同步测量,结合非定常传热分析,获得了超临界压力下、亚/超临界温度范围内煤油的流动和传热物理参量的变化曲线。     

Electrical Characteristics of Silicon Solar Cells at Low Temperatures

Experimentally determined values of open-circuit voltage, short-circuit current, and maximum power for p on n and n on p silicon solar cells are presented for temperatures ranging from -196°C to + 50°C under equivalent space sunlight intensities of 58 mW/cm2 and 268 mW/cm2. An anomalous behavior is observed in the n on p cells at low temperatures; namely, the open-circuit voltage becomes nearly independent of temperature below a transition temperature Tt that depends on the sunlight intensity.