IOP Conference Series: Materials Science and Engineering

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ISSN / EISSN : 17578981 / 1757899X
Current Publisher: IOP Publishing (10.1088)
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T Balachandran, D Lee, N Salk, Kiruba S. Haran
IOP Conference Series: Materials Science and Engineering, Volume 756; doi:10.1088/1757-899x/756/1/012030

Partial and fully superconducting (SC) machines promise high power density capabilities required for electric propulsion. These machines need to achieve high power densities while reducing electrical heat losses to minimize the required cryogenic power and subsequent additional weight. Hydrogen powered all-electric planes provide a design space where ac losses are manageable. However, the high electrical frequencies in high-speed fully superconducting machines pose a significant challenge to reducing armature ac losses. In high-speed applications, coupling loss in the SC armature coils dominates and becomes a barrier for practical application of these machines. In this paper a fully superconducting machine is proposed for a hydrogen powered regional all-electric plane. An air core design is considered utilizing low ac loss MgB2 wires. The design is targeted to achieve 50 kW/kg specific power while requiring ac losses to be less than 3 kW. This study explores the possibility of replacing a passive iron shield with active shielding coils to contain the magnetic flux inside the machine while reducing weight and increasing power density. The study focuses on minimizing weight as well as ac losses in the armature coils. An optimization algorithm is used to determine the trade-offs between iron shield and active shield coil designs. Results show that optimal designs for electric propulsion eliminate the passive shield in favor of active shielding coils - increasing the power density of the machine while maintaining the outside flux density below standard safety limits.
W A Holmes, E Boehmer, C Bertagne, S Cheung, B Cho, H Cho, G Delo, R P Dillon, M Farris, A Feizi, et al.
IOP Conference Series: Materials Science and Engineering, Volume 755; doi:10.1088/1757-899x/755/1/012017

We describe the design and testing of the Cryogenic Flex Cable (CFC) delivered for the Near-Infrared Spectro-Photometer (NISP) instrument [1] for the ESA Euclid mission [2, 3]. The Euclid spacecraft is scheduled for launch in the summer of 2022. It will observe ~ 1/3 of the total sky using a telescope with 1.2m SiC primary mirror, passively cooled to ~ 125K, and containing Visible Imager (VIS) [4] and NISP focal plane instruments, from an orbit at the Earth-Sun L2 lagrange point. At the heart of the NISP instrument is a 4X4 mosaic focal plane of Teledyne H2RG infrared detector arrays held at 100K. The CFC described here are designed to link each detector array to a dedicated packaged cryogenic electronics assembly held at ~ 137K with minimal heat leak to the 100K stage and to withstand handling and launch vibrations. Prototype CFCs were developed and tested by Teledyne. The final 7-layer CFC flexible printed circuit boards and Airborn nanoconnectors were provided by Teledyne and assembled for flight at the Jet Propulsion Lab (JPL). Flight qualification CFC were made and subjected to thermal conductance, thermal emissivity, thermal cycle, survivability to bend, vibration and normal mode testing at JPL. The flight CFC were subject to bake out and thermal cycle at JPL and then tested with the flight detectors and electronics at Goddard Space Flight Centers Detector Characterization Lab. The results of the qualification tests as well as the measured characteristics of the 41 manufactured CFC are summarized.
A Nishimura
IOP Conference Series: Materials Science and Engineering, Volume 756; doi:10.1088/1757-899x/756/1/012013

Superconducting magnets for fusion application will be irradiated by fast neutrons produced by fusion reaction, and it has been reported that the superconducting properties of the superconducting wires vary drastically by the irradiation. A bronze route Nb3Sn wire and an internal tin process wire were irradiated in a fission reactor up to 1.7 × 1023 n/m2 (> 0.1 MeV neutron), and the change in the critical current was measured by 15.5 T superconducting magnet and a variable temperature insert. The 4.9 × 1022 n/m2 irradiation for the bronze route wire increased the critical current by 1.75 times, but the 7.9 × 1022 n/m2 irradiation showed 1.03 times increase for the bronze route wire and 0.72 times decrease for the internal tin process wire. The 1.7 x 1023 n/m2 irradiation for the internal tin process wire decreased the critical current severely and the critical magnetic field down to around 16 T. This was the first result that the high fluence neutron irradiation caused the degradation of both the critical current and the critical magnetic field in this type of a Nb3Sn wire. Some irradiation defects will become the magnetic flux pining sites and strengthen the pining force. But the strong irradiation will damage the superconducting phase and degrade the properties.
A Kashani, D Hauser, P Desai
IOP Conference Series: Materials Science and Engineering, Volume 755; doi:10.1088/1757-899x/755/1/012006

Current proposed NASA missions to Moon and Mars involve producing cryogenic propellant in-situ to reduce launch mass and requirements. One technique for liquefaction of the gases produced through electrochemical processes is to circulate cold gaseous neon or helium through broad area cooling tubes attached to the outside of the propellant tanks. To determine the performance of this liquefaction process tests are being conducted at NASA Marshall Space Flight Center in a 4.25 cubic meter tank with a broad area cooling network. A transient computational fluid dynamic code coupled with a thermal model of the tank and its cooling loops is developed in Thermal Desktop to compare against the results of these tests. Details of the model and the model predictions and comparison to experimental data from recent liquefaction tests are presented here.
J Mondal, A Mishra, R Lakkaraju, M AshokKumar, P Ghosh
IOP Conference Series: Materials Science and Engineering, Volume 755; doi:10.1088/1757-899x/755/1/012066

Multiple bubble interactions in initially quiescent liquid are often accompanied by generation of jets, shockwaves and light. At cryogenic temperature (< 123 K) when certain materials (particularly bcc-type) become brittle, such afore-mentioned physical effects can be effective in disintegrating them to smaller fragments. CFD techniques based on direct numerical simulations can help to understand this phenomenon that may benefit nanotechnology-based industries and oil-gas exploration-firms working with air-gun arrays. In this paper, multiple bubble-pairs are simulated in a co-centric manner around a centrally located solid target (5 mm radius). The ambient fluid is liquid nitrogen (77 K) and the bubbles are gaseous nitrogen (87 K). 2D numerical simulation using the VOF method in compressible domain is carried out neglecting the effect of phase change and gravity. The stand-off distance between the solid target and bubble-pairs are varied systematically and its influence on the fluid-dynamic effects (e.g. pressure shockwave & jets) are compared. Initial calculations suggest that for stand-off distance of 0.93 mm, shockwaves measure above 10 times the ambient pressure and liquid jet speeds around 30 m/s in cryogenic environment, at multiple locations very close to the solid target. These consecutive physical impacts can foster ample liquid-hammer pressures, making it promising for solid wear at 77 K when juxtaposed against room-temperature cases.
J Wang, C Z Pan, T Zhang, K Q Luo, X T Xi, L B Chen, Y Zhou
IOP Conference Series: Materials Science and Engineering, Volume 755; doi:10.1088/1757-899x/755/1/012036

Vuilleumier cycle was first patented in 1918. It was usually regard as the thermal-driven Stirling refrigeration cycle, which combined the low-frequency working pattern like Giffod-Mcmahon (GM) cryocooler and the compactness of Stirling-type cryocooler. With the continuous development in the past 100 years, the Vuilleumier-type (VM-type) cryocoolers have to been proved to generate cooling power from ambient temperature to liquid nitrogen temperature and even to liquid helium temperature. In recent decades, some efforts were made on traditional displacer-type VM cryocooler, Vuilleumier hybrid pulse tube cryocooler (VM-HPTC) and the VM-type pulse tube cryocooler (VM-type PTC) to obtain the liquid helium temperature. Successfully, not only the 4 K was obtained, but also the limit temperature of oscillating cryocooler by He4 was hit. This paper presents the progress of the 4 K-class VM-type cryocooler and analyzed the possible applications of 4 K class VM-type cryocooler.
A Al-Taie, S Telikapalli, P Cheetham, C H Kim, S V Pamidi
IOP Conference Series: Materials Science and Engineering, Volume 756; doi:10.1088/1757-899x/756/1/012033

In an attempt to eliminate solid insulation challenges in cryogenic superconducting power cables, a new design concept for liquid cryogen cooled superconducting power cable was investigated. The design is based on superconducting gas insulated line (S-GIL). The design used liquid cryogen as the sole insulation medium. The suitability of the design for medium voltage power cables is discussed and the benefits of eliminating a solid insulation were identified. Experiments on 1-m long model cables with insulator tubes as spacers showed that the design is suitable for cables at 50 kV or higher. The actual limits could not be identified because of the experimental limitations originated from limited standoff distances in the measurement setup used. On a fundamental level, the investigations presented in the study showed a direct correlation between the intrinsic dielectric strength of the cryogen used and the maximum tolerated voltage for a given diameter of the cable system. The results show the promise for liquid nitrogen (LN2) and liquid hydrogen (LH2) cooled cables for various medium voltage applications, including electric aviation and electric ships.
V Ilardi, L N Busch, A Dudarev, T Koettig, P Borges De Sousa, J Liberadzka, H Silva, H H J Ten Kate
IOP Conference Series: Materials Science and Engineering, Volume 756; doi:10.1088/1757-899x/756/1/012005

The Future Circular Collider (FCC) study includes the design of the detector magnets for the FCC-ee+ (electron-positron) collider, requiring a 2 T solenoid for particle spectrometry, and for the FCC-hh (proton-proton) collider, with a 4 T detector solenoid. For both solenoids and their cryostats, CERN is developing an innovative and challenging design in which the solenoids are positioned inside the calorimeters, directly surrounding the inner tracker. For this purpose, the cryostats must be optimized to have maximum radiation transparency. They are structured as a sandwich of thinnest possible metallic shells for achieving vacuum tightness, supported by layers of low density and highly radiation transparent insulation material, still providing sufficient mechanical resistance and low thermal conductivity. In this respect, thermal and mechanical analysis of innovative insulation materials are currently being carried out. The first material of interest, Cryogel® Z, is shaped as a flexible composite blanket, which combines silica aerogel with reinforcing fibers and a density of 160 kg/m3. It allows a 4 m bore, 6 m long FCC-ee+ detector solenoid cryostat with a total thickness of 250 mm. CERN has investigated the compression of Cryogel® Z under 1 bar equivalent mechanical load and its thermal conductivity between 10 K and room temperature, as well as the critical phenomena of thermal shrinkage and outgassing. We present the test results, as a first overview on the material.
B Nitin, Pavitra Sandilya, Goutam Chakraborty
IOP Conference Series: Materials Science and Engineering, Volume 755; doi:10.1088/1757-899x/755/1/012054

Dewars are used to store and transport cryogens like LNG, LN2, LOX, LHe etc. These comprise two vessels, one placed inside the other and held together either at the "neck" (input/output port) or by support systems, depending on the capacity, the mechanical loads on the vessel and the boil-off characteristic of the stored cryogen. Support system based dewars are more common for real-life and industrial applications. Design of the support system are based on the principles that are used for high temperature pressure vessels. On the other hand, support system to be used for cryogenic fluid storage should also address the heat inleak through the supports along with the imposed mechanical load and thermal contraction-expansion effects. Some safety factors are prescribed in the literature to address these concerns; however, the scientific basis of design strategies available in the open literature so as to give a more scientific basis of design is absent. This would result in reduction in use of excessive dimensions or material thereby reducing the payload and the capital cost. Considerations of mechanical load and thermal heat inleak often lead to diametric conclusions in terms of the diameter/thickness of the support system, leading to pareto-optimal solution. Topology optimization (TO) is often used to design structures like bridges, vehicles, robotic arms etc. by a systematic and sequential removal of the mass of the material being used to fabricate the given structure while meeting the constraints in terms of load bearing capacity of the structure and heat inleak. This methodology may be followed to arrive at an optimized geometry for the support system when the designer is unsure of the initial shape to start working. In this work, TO has been tested with various thermal and mechanical boundary conditions to arrive at optimized support geometry.
J Fydrych, S Pietrowicz
IOP Conference Series: Materials Science and Engineering, Volume 755; doi:10.1088/1757-899x/755/1/012100

Large scientific facilities applying HeII technologies usually use the Joule-Thomson expansion for the final production of saturated superfluid helium at their cryogenic users. The users are usually supplied with subcooled liquid helium at 4.5 K and 3 to 4 bar(a). Then, to produce HeII, the 4.5 K helium is precooled in a local heat exchanger and throttled to a subatmospheric pressure below 50 mbar(a). This final throttling goes along an isenthalpic line which leads to the zone of wet vapour at the quality of 15.9%. The efficiency of this process can be strongly affected by additional heat loads, which may result in a significantly higher quality of the throttled helium. This imperfection can be partly decreased by using a local subcooler or by splitting the expansion process into two phases with an intermediate point around 1.2 bar(a). However, these solutions require additional components, such as phase separators with some instrumentation and another throttling valve. The paper presents the comparative thermodynamic analysis of the three identified cooling loops. Potential savings due to thermodynamic efficiency improvements are verified against the capital costs for different operation times.
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