Numerical analysis of the static performance of an annular aerostatic gas thrust bearing applied in the cryogenic turbo-expander of the EAST subsystem

The EAST superconducting tokamak, an advanced steady-state plasma physics experimental device, has been built at the Institute of Plasma Physics, Chinese Academy of Sciences. All the toroidal field magnets and poloidal field magnets, made of NbTi/Cu cable-in-conduit conductor, are cooled with forced flow supercritical helium at 3.8 K. The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of coils, structures, thermal shields, bus-lines, etc. The high-speed turbo-expander is an important refrigerating component of the EAST cryogenic system. In the turbo-expander, the axial supporting technology is critical for the smooth operation of the rotor bearing system. In this paper, hydrostatic thrust bearings are designed based on the axial load of the turbo-expander. Thereafter, a computational fluid dynamics-based numerical model of the aerostatic thrust bearing is set up to evaluate the bearing performance. Tilting effect on the pressure distribution and bearing load is analyzed for the thrust beating. Bearing load and stiffness are compared with different static supply pressures. The net force from the thrust bearings can be calculated for different combinations of bearing clearance and supply pressure.

ADS Injector-I 2 K superfluid helium cryogenic system

The Accelerator Driven Sub-critical(ADS)system is a strategic plan to solve the nuclear waste problem for nuclear power plants in China.High-energy particle accelerators and colliders contain long strings of superconducting devices,superconducting radio frequency cavities,and magnets,which may require cooling by 2 K superfluid helium(HeliumⅡ).2 K superfluid helium cryogenic system has become a research hot spot in the field of superconducting accelerators.In this study,the ADS Injector-I 2 K cryogenic system is examined in detail.The cryogenic system scheme design,key equipment,and technology design,such as the 2 K Joule–Thomson(J–T)heat exchanger and cryomodules CM1+CM2 design,are examined,in addition to the commissioning and operation of the cryogenic system.The ADS Injector-I 2 K cryogenic system is the first 100 W superfluid helium system designed and built independently in China.The ADS proton beam reached 10 Me V at 10 m A in July 2016 and 10 Me V at 2 m A in continuous mode in January 2017 and has been operated reliably for over 15,000 h,proving that the design of ADS Injector-I 2 K cryogenic system,the key equipment,and technology research are reasonable,reliable,and meet the requirements.The research into key technologies provides valuable engineering experience that can be helpful for future projects such as CI-ADS(China Initiative Accelerator-Driven System),SHINE(Shanghai High Repetition Rate XFEL and Extreme Light Facility),PAPS(Platform of Advanced Photon Source Technology),and CEPC(Circular Electron-Positron Collider),thereby developing national expertise in the field of superfluid helium cryogenic systems.

Present status and one upgrading method with a cold compressor of the EAST sub-cooling helium cryogenic system

Since 2006, the superconducting toroidal field（TF） coils of the Experimental Advanced Superconducting Tokomak（EAST） have been successfully cooled by supercritical helium at a temperature of 4.5 K and a pressure of 4 bara in eleven experiments. To obtain higher operating currents and magnetic fields it is necessary to lower the operating temperature of the TF coils.The EAST sub-cooling helium cryogenic system, with a warm oil ring pump（ORP）, was tested twice in cool-down experiments, which made the TF coils operate at 3.8 K. However, the long term operational stability of the sub-cooling system cannot be guaranteed because of the ORP＇s poor mechanical and control performance. In this paper, the present status of the EAST subcooling helium cryogenic system is described, and then several cooling methods below 4.2 K and their merits are presented and analyzed. Finally, an upgrading method with a cold compressor for an EAST sub-cooling helium cryogenic system is proposed. The new process flow and thermodynamic calculation of the sub-cooling helium system, and the main parameters of the cold compressor, are also presented in detail. This work will provide a reference for the future upgrading of the sub-cooling helium system for higher operation parameters of the EAST device.

The Application and Improvement of Helium Turbines in the EAST Cryogenic System

The helium cryogenic system supplies supercritical helium cooling capacity at 4.5 K for the superconducting magnets in the EAST superconducting tokamak.Four low-temperature helium turbines are used in the 2 kW helium refrigeration system,and their performance and reliability are critical for the continuous operation of the tokamak.The turbines were made by the Helium Mechanics Company in Russia.The start-up process is very unstable,easily broken,and thus testing and improvements are needed.In this paper,we analyze the structure of the helium turbine,make improvements,and describe the testing process and results of the improved helium turbines.Some of the operational experiences during the start-up process and tests are also presented.

Cryogenic system design for HIAF iLinac

A helium cryogenic system is designed by the Institute of Modern Physics,Chinese Academy of Sciences,to supply different cooling powers to the cryomodules of ion-Linac(iLinac)accelerator,which serves as the injector of the High Intensity Heavy-Ion Accelerator Facility project.The iLinac is a superconducting heavy-ion accelerator approximately 100 m long and contains 13 cryomodules cooled by superfluid helium.This article describes the cryogenic system design of the iLinac accelerator.The requirements of the cryogenic system,such as cooling mode,refrigeration temperature,operating pressure and pressure stability,are introduced and described in detail.In addition,heat loads from different sources are analyzed and calculated quantitatively.An equivalent cooling capacity of 10 kW at 4.5 K was determined for the cryogenic system according to the total heat load.Furthermore,a system process design was conducted and analyzed in detail.Further,the system layout and the main equipment are presented.

Optimization Analysis and Simulation of the EAST Cryogenic System

This paper presents the optimization cycle of the EAST cryogenic system. A simulation analysis and simulation of the main Claude program of this cycle was developed on the basis of the characteristics of the components and verified with the experimental results. The built-in volume ratio of the No. 7 compressor was tested with the purpose of finding the optimum internal pressure ratio to comply with the external pressure ratio so as to increase the isothermal efficiency and cycle efficiency. In addition, the UA （U, heat transfer coefficient; A, heat transfer area） values of the heat exchangers, efficiencies of turbines, mass flow fraction of the turbine stream were analyzed in order to improve the capacity or efficiency of the cycle. Finally, in view of the estimated heat loads of EAST in future, an upgraded operational cycle of 1500 W/4.5 K ＋1000 W/3.5 K ＋5 g/s is proposed according to the simulation.

氦低温透平膨胀机热力性能数值模拟与实验测试

为了深入研究氦透平膨胀机在降温过程及低温条件下的热力学特性,依托ADS 500 W/4.5 K低温制冷机建设了80 K温区的实验系统,进行了氦透平膨胀机的低温变工况测试。测试的氦透平膨胀机主轴轴径为12.00 mm,采用动压氦气体轴承支承,最高转速可以达到252130 r·min^(-1)。在膨胀比为1.88时,膨胀机最大出口温降达到8.1 K;在膨胀比为2.07时,等熵效率达到最高值71.2%。以实验用氦透平膨胀机尺寸及测试工况为基础,建立了透平的数值模型。采用商业软件ANSYS CFX对透平的热力性能及降温特性进行了数值模拟,得到了相应的理论温降曲线。研究结果表明:所建数值模型能够较好地预测该氦透平膨胀机的温降过程,膨胀机出口温度的实验值和计算值结果最大相对偏差为0.45%;所测试的低温氦透平具有优良的热力性能和降温特性,测试的动压氦气体轴承表现出良好的支承稳定性,数值计算和实验结果可为后续相关研究和大科学装置的应用提供参考。

基于减压降温原理的超流氦获取真空机组的研制

南方先进光源研究测试平台(SAPS-TP)为了给超导腔提供2 K测试环境,采用在氦池入口抽真空至饱和蒸气压的方式来获取2 K超流氦。研制一套减压降温真空机组用来抽取真空,详细介绍了设计和选型计算,并借鉴各大型2 K低温系统的使用经验,进行了优化。已完成20余次超导腔的性能测试,真空机组运行稳定,氦池压力、温度和液位等参数的控制精度达到设计指标。运行测试结果表明,所研制的减压降温真空机组性能满足设计要求。

基于多级闪蒸与多塔蒸馏耦合的贫氦天然气低温提氦工艺

聚焦从低品位含氦天然气中提纯氦气这一工程问题,在分析已有深冷工艺发展现状与改进方向的基础上,针对原料天然气中氦气浓度低与提氦能耗高的问题,提出一种基于多级闪蒸与多塔蒸馏耦合的贫氦天然气低温提氦工艺,并借助ASPEN HYSYS软件模拟设计了新工艺流程。结果表明:采用设计工艺可从氦摩尔分数为0.05%的贫氦天然气中分离得到纯度(摩尔分数,下同)为99%的氦气,同时得到纯度为99.96%的甲烷和99%的氮气、液化天然气及燃料气,增强了提氦装置的产品方案灵活性;通过工艺内部流股节流膨胀制冷为分离系统提供冷量及工艺内部冷热物流间合理匹配换热,实现了系统的节能降耗;该多级闪蒸+多塔蒸馏耦合工艺的单位压缩功耗为0.058 kW·h kmol,远低于改进型ExxonMobil公司的提氦工艺(1.29 kW·h kmol);综合分析工艺产品纯度及能耗,说明设计的提氦工艺具有一定的应用潜力。

1.8~300 K温区温度计标定平台设计与测试分析

核聚变装置通常在超低温环境下运行,对温度的精确测量有着严苛的要求。超低温环境下的温度精确测量与标定直接影响着核聚变、高能物理、航空航天等涉及超低温环境的研究领域的发展。根据聚变堆主机系统综合研究设施CRAFT的测试条件,设计了液氦温度计标定平台,可开展1.8~300 K温区内的温度标定与实验研究。该平台通过吉福德-麦克马洪循环制冷机(GM制冷机)以及毛细管节流制冷,实现样品腔降温至1.8 K;通过调节加热器功率控制样品腔温度,可实现1.8~20 K温区内±5 mK波动、20~300 K温区内±15 mK波动的温度环境条件。使用低温测量控制设备对标定区域进行不同温度点位的控温和数据采集,最终得到标定精度结果为:1.8~4.2 K时为±9.54 mK;4.2~20 K时为±22.44 mK;20~300 K时为±346.78 mK。

氦低温系统关键参数及流程优化研究进展

氦低温系统应用于极低温技术领域,高效节能的氦低温系统将极大推动低温超导技术的发展。因此,研究系统中主要部件对其性能的影响、针对系统中主要热力学参数进行遗传算法优化,对提高系统制冷效率和经济效益以及保持其长期运行的稳定性十分重要。基于此,对国内外氦低温系统主要影响部件膨胀机和换热器的关键参数以及[火用]分析和遗传算法优化进行了梳理分析,总结了现存技术难点和发展趋势。

锯齿型翅片内不同温区氦气流动与传热性能对比及节距对翅片性能影响的研究

为分析板翅式换热器在低温工况下的流动换热性能与常温工况下的差异和翅片节距对其性能影响,建立氦气在锯齿翅片通道内流动与传热的数值模型,开展数值模拟分析。结果表明:低温氦气在锯齿型翅片通道内的传热性能优于常温氦气。在氦气入口温度为20 K时,j因子比300 K时提升1.1%~55.9%,比77 K时提升0.41%~13.01%;在氦气入口温度为77 K时,j因子比300 K时提升0.53%~38.47%。低温氦气在锯齿型翅片通道内的流动性能比常温氦气差。在氦气入口温度为20 K时,f因子比300 K时高16.84%~28.87%,比77 K时高3.98%~23.19%。翅片节距大小在不同温区下对翅片流动与传热性能均有显著影响。在不同温区下,j因子随着翅片节距增大而减小,f因子随着翅片节距减小而增大。低雷诺数时,JF因子随着翅片节距减小而增大,而高雷诺数时则出现相反的趋势。

天然气粗氦提取技术进展及展望

氦气是一种关系国家安全和高新技术产业发展的战略性资源。空气中氦含量仅有5.2 mL/ m^(3),而含氦天然气中的氦含量可以达到0.3%~8%,虽然可利用大型空气液化分离装置的不凝气进行工业化分离生产氦气,但从含氦天然气中提取氦气在经济上更具可行性,也是目前氦气的最主要来源。从含氦天然气中提取氦气,首先要将含氦天然气中大部分甲烷、氮气等组分脱除,提取粗氦,然后再进行粗氦精制。介绍了深冷技术、膜分离技术、膜分离及深冷联合技术、多联产技术等多种粗氦提取技术,并对未来发展适应中国国情的贫氦天然气低成本提氦成套技术与装备国产化提出了展望。

国内氦液化储运技术需求分析

为满足国内用氦需求的快速增长,有效保障国内的用氦安全和相关产业的平稳运行,从提氦液化技术、氦液化储存技术、液氦运输技术和产品应用等方面对国内氦液化和储运技术需求进行了分析,并对终端用户对液氦和氦回收技术需求进行介绍。与其他提氦工艺相比,深冷液化提氦具有效率高、纯度高,与下游储运流程兼容性好等优点,是目前全球应用最广泛的天然气提氦技术;液化储氦与高压氦气和储气库相比具有效率高、安全性高、纯度高和损耗少等优点;液氦在长距离、大容量运输方面优势较明显;40%以上的终端用户以液氦为介质,为避免氦资源损失,需保证液氦的有效利用、气化部分及时回收再液化。因此,氦液化技术和液氦储运技术是解决目前国内氦短缺和有效利用的关键,需要在提高国产关键设备性能和降低成本方面实现技术突破。

Simulation study on thermal performance of two turns helium cryogenic oscillating heat pipe for superconducting accelerator

Purpose In recent years,with the further development of superconducting technology,superconducting devices have been applied in particle accelerators and synchrotron radiation light source devices.As a new type of heat transfer structure,helium cryogenic oscillating heat pipe can be used to balance local hot spots in superconductors and improve heat transfer performance.Methods In this paper,a two-dimensional two-turns helium cryogenic oscillating heat pipe model is established.The flow performance of helium cryogenic oscillating heat pipe was analyzed by CFD simulation.Results and conclusion The results show that the development of flow pattern in the helium cryogenic oscillating heat pipe first forms bubble flow under the heating of the evaporation section,and then gradually forms slug flow and annular flow.The process consists of initial stage,transition stage and running stage.In the running stage,the effective thermal conductivity of COHP oscillates around 15,000 W/(m·K).

Process Modeling and Dynamic Simulation for EAST Helium Refrigerator

In this paper,the process modeling and dynamic simulation for the EAST helium refrigerator has been completed.The cryogenic process model is described and the main components are customized in detail.The process model is controlled by the PLC simulator,and the realtime communication between the process model and the controllers is achieved by a customized interface.Validation of the process model has been confirmed based on EAST experimental data during the cool down process of 300-80 K.Simulation results indicate that this process simulator is able to reproduce dynamic behaviors of the EAST helium refrigerator very well for the operation of long pulsed plasma discharge.The cryogenic process simulator based on control architecture is available for operation optimization and control design of EAST cryogenic systems to cope with the long pulsed heat loads in the future.

Study on the Dynamic Performance of the Helium Turboexpander for EAST Subsystems

An increase of the cooling capacities in the liquid helium temperature area is re- quired by Experimental Advanced Superconducting Tokamak （EAST） due to the extension of its subsystems in the near future. Limited by the heat exchangers, cryogenic pipes, and cryogenic valves, it is difficult to enlarge the present EAST helium system. 102 W@4.5 K level helium cryogenic systems are needed in view of feasibility and economy. A turboexpander is the key com- ponent of a helium cryogenic system. In this article, a hydrostatic gas lubricated cryogenic helium turboexpander for a 900 W@4.5 K cryogenic helium system was developed for the EAST updated subsystem by the Institute of Plasma Physics, Chinese Academy of Sciences and the Institute of Cryogenic and Refrigeration of Xi＇an Jiaotong University. The main components, such as gas bearings, expansion wheel, shaft, and brake wheel, were briefly presented. The dynamic perfor- mance of the journal and thrust gas bearings was investigated numerically. The rotordynamic performance of the developed turboexpander was studied experimentally. The results show that the axial and radial load capacities supplied by the journal gas bearing and thrust gas bearing are enough to balance the axial force and radial force of the rotor. A 43% overspeed operation was achieved, which validated the reasonable design of the turboexpander.

深冷法提氦联产LNG工艺分析优化

为提高天然气提氦的经济性,基于深冷法提氦流程,提出一种天然气氦气回收及天然气液化联产工艺。由于提氦流程换热结构的复杂性,利用传统㶲分析对工艺设备的㶲损和㶲效率进行定量分析,通过高级㶲分析对设备的真实改进潜力进行评价。传统㶲分析结果显示:工艺主要设备㶲效率普遍较高;氦提浓冷箱E-101是工艺中㶲损最大的设备,占总㶲损量的35.56%。高级㶲分析结果显示:工艺系统中主要设备的㶲损失大部分为内源性㶲损,表明改进的重点应放在每个独立设备的优化上,比如通过改变混合冷剂增压装置C-101效率等方式来减少㶲损。研究为天然气氦回收工程优化设计及应用提供了技术参考。

联产乙烷天然气提氦工艺的经济性与适用性分析

为提高氦气开发的程度,提高天然气中氦气的提取率,将乙烷回收工艺与深冷-膜分离提氦工艺相结合,得到联产乙烷的天然气深冷-膜分离提氦技术。经验证,回收率能够达到工艺设计要求。经济性与适用性分析结果表明,在相同操作条件下,联产乙烷的天然气深冷-膜分离提氦工艺相比于天然气提氦工艺与乙烷回收工艺的总压缩能耗、综合能耗及单位综合能耗均低20%;且在乙烷含量、含氦量、处理量等波动时,都有较好的适用性。

联产乙烷的天然气提氦工艺研究

为了解决单一的天然气深冷分离提氦工艺中设备能耗大、投资大、效率低的问题,将天然气深冷分离提氦工艺与膜分离提氦工艺结合以提高氦体积分数与回收率,同时结合天然气乙烷回收工艺实现冷能的最大化利用,建立了联产乙烷的天然气深冷-膜分离提氦工艺。利用HYSYS软件对联产乙烷的天然气深冷-膜分离提氦工艺与单一的天然气乙烷回收工艺和深冷-膜分离提氦工艺进行流程模拟。模拟结果表明,4种典型乙烷回收工艺中气体过冷工艺的乙烷回收率最高,可达90.13%;将天然气深冷分离提氦工艺与膜分离提氦工艺结合后氦体积分数由66.77%提高到了99.6%;联产乙烷的天然气深冷-膜分离提氦工艺可以有效地集成回收和利用冷量,相较天然气深冷-膜分离提氦工艺+部分干气循环工艺,总压缩能耗低23.10%,单位综合能耗低20.46%。