超导直流能源管道本体是实现电力/液化天然气一体化输送的关键部件,承担着能源输送、高效热耦合和主动安全防御等功能.对超导直流能源管道原理验证样机进行了实验测试和仿真分析,获得了稳态运行时的管道沿程温度分布,其中出口温度测量值为95.5 K,仿真计算值为95.18 K.沿程温度分布仿真值和测量值偏差不超过1％,验证了仿真模型的正确性和仿真方法的有效性.基于实验验证的仿真模型和方法,对四种典型的能源管道本体结构进行了仿真分析.对比不同管道结构的温度场和流场仿真结果,获得了各种管道结构的特点,为超导直流能源管道的设计和优化提供了理论指导.

Nitrogen / carbon tetrafluoride (N2/CF4) may have a feasibility for use as the coolant or insulator of power apparatus but few studies have been carried out to figure out the characteristics of it. In order to have a better understanding of such mixture, some molecular features and properties concerning N2, CF4 and their compound are calculated through computational quantum chemistry methods and discussed in this paper with the emphasis focusing on molecular surfaces and intermolecular interactions. Concretely, the phase equilibrium curves are predicted according to several parameters obtained through the analysis of molecular surfaces. Furthermore, surface electrostatic potentials (ESPs) are studied and the mutual interpenetration distance was obtained. In addition, in order to have a further understanding of intermolecular interactions between N2 and CF4, the density of states (DOS) and charge decomposition analysis (CDA) are discussed as well as an analysis of electron density difference (EDD) and quantum theory of atoms in molecules (QTAIM). Finally, a prediction of electric strength is performed and it could be found from the prediction that N2/CF4 has an electric strength superior to N2 but inferior to CF4.

Y A superconducting energy pipeline is an integrated system for fuel delivery and power transmission. In the energy pipeline, direct current (DC) power is carried by superconducting tapes with almost no loss. Moreover, liquefied natural gas (LNG) is used not only as one kind of clean energy but also as a cooling medium. However, the lack of data on the electrical insulation characteristics of LNG (especially the resistance to breakdown and flashover) restricts the development of a superconducting energy pipeline. Therefore, this paper focuses on solving a series of problems (such as gas tightness, overpressure, and high voltage) in LNG insulation testing, obtaining the electrical failure data of multicomponent LNG, and analyzing the behavior of electric breakdown and flashover in LNG. The test results show that LNG as a dielectric cooling medium has remarkable performance in withstand voltage to replace the liquid nitrogen/liquid tetrafluoromethane (LN2/LCF4) binary mixtures. The research could offer key technical support for the superconducting energy pipeline and also provide a reference for the study of electrical properties on other cryogenic fuels.

将超导输电技术与液化天然气(LNG)管道输送技术相结合,形成能同时输送LNG与电力的能源管道,不仅可以节约能源通道,还可以利用LNG冷却超导电缆,提高能源输送效率和经济性,是一种极具前景的能源输送方式.在国家"智能电网与装备"重点研发计划的支持下,开展了超导直流能源管道的基础研究.该文主要介绍超导直流能源管道的基础研究项目近一年多的进展情况,主要包括:LNG混合工质的低温液固转变机理及传热流动特性,电力/LNG一体化输送动态稳定性判据,为安全性与故障演化分析而搭建的实验平台及初步实验结果,以及10m/10kV超导直流能源管道原理样机的研制与实验情况.

The insulation design of superconducting power equipment requires liquid dielectric with excellent electrical and thermal characteristics at cryogenic temperatures. Many liquid dielectrics have been used for cooling the superconducting materials, a potential choice being chlorotetrafluoroethane (R124), due to its good thermal conductivity. However, its electrical characteristics at low temperatures are yet to be investigated. In this paper, devices for measuring the volume resistivity and electrical intensity of R124 are designed and the prototypes are built. The changes in the volume resistivity and breakdown with respect to the parameters such as temperature and electric field are measured. It is observed that at low temperatures and with low strength electric fields, the volume resistivity of the R124 decreases rapidly with increase in the temperature. Conversely, its value increases with the increase of electric field strength. Also, it is observed that the breakdown field strength increases with the decrease of temperature. However, when R124 breaks down at high voltages, carbon deposition takes place, and thus, it cannot be used for cryogenic liquid insulation.

HighT(c)superconducting (HTS) DC cable is a promising solution for large-scale power transmission over long distance. However, the refrigeration system for HTS cable is indispensable but undesirable. Considering that LNG (liquid natural gas) is now one kind of clean energy that is used more and more widely, it is possible to integrate HTS cable and LNG transportation into a single pipeline, resulting in a new energy transportation system- a HTS energy pipeline. In this paper, the principle and structure of the energy pipeline are first discussed and then the basic physical properties of the HTS tapes and liquid insulation medium in the LNG temperature range are analyzed. On this basis, a 10 kV/1 kA energy pipeline is designed, fabricated and tested.

•Based on the requirement of integrated transportation of electricity and LNG, an effective structure with high safety and efficient heat exchange is proposed.•The HTS tape and insulation medium used in LNG temperature range are discussed.•Based on the comparison of different types of bipolar cable and pipeline, the overall design scheme of ±100 kV/1 kA superconducting DC energy pipeline with optimized comprehensive performance is given.

Superconducting DC energy pipeline is an energy channel that simultaneously transmits electrical energy as well as the liquid fuel. It improves the efficiency of energy transmission and reduces the overall cost by cooling high-temperature superconducting DC cables with the low-temperature liquid fuel, such as liquid hydrogen, liquefied shale gas, and liquified natural gas (LNG). In order to properly design this, it is very important to know the temperature distribution along the pipeline, which is yet to be carried out by the researchers. In this paper, a 10 m energy pipeline with LNG cooling and having a concentric nested structure is simulated and tested experimentally. The simulation results of the temperature rise along the pipeline were in good agreement with the experimental results. The effect of various parameters on the pipeline temperature were also obtained. Finally, based on the theoretical equations and simulation results, an empirical formula is proposed to calculate the temperature at the outlet of the energy pipeline.

It is usually difficult to obtain the radial levitation force of the radial-type superconducting magnetic bearing (SMB) due to the massive numerical calculations and the sophisticated experimental measurements. This study presents a method for fast calculating the radial levitation force of radial-type SMB, which is based on the infinitesimal method and the 2D finite-element method. During the modelling, the radial-type SMB is assumed to be composed circumferentially of infinite superconductor-permanent magnet (SC-PM) infinitesimals with shape of rectangular thin slice. The dependence of levitation force for the SC-PM infinitesimal on the air-gap length between the SC stator and the PM rotor can be obtained using the 2D finite-element model established in Cartesian coordinate system. Moreover, a simplified analytical model of calculating radial levitation force is developed based on the infinitesimal method and the circumferential distribution formula of non-uniform air-gap when the PM rotor exhibits radial eccentricity. The results of theoretical calculation and experimental measurement of radial levitation force show a good agreement, which verifies the feasibility of the proposed method. It has the advantages of fastness and easiness, and can be used as a theoretical tool for the design, optimisation and performance prediction of the radial-type SMB.