• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.907-912
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• 2001

KOGAS had developed the Ring-knot membrane for LNG storage tank. But we found that some modifications were needed in using the Ring-knot membrane for the commercial LNG storage tanks. So, both analytical and experimental studies have been performed to investigate the strength of the new membrane and the reaction force at the anchor point. Using nonlinear FEM code and experiments, the stress analysis of the new corrugated membrane shapes subject to the cryogenic liquid pressure and thermal loading are performed to ensure the stability and fatigue strength of the new membrane. This paper reports on the results of investigations into this new type of membrane.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.149-150
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• 2005

According to the trend for electric power equipment of high capacity and reduction of its size, the needs for the new high performance electric equipments become more and more important. On of the possible solution is high temperature superconducting (HTS) power application. Following the successful development of practical HTS wires, there have been renewed activities in developing superconducting power equipment. HTS equipments have to be operated in a coolant such as liquid nitrogen ($LN_2$) or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of unfilled epoxy and filled epoxy in $LN_2$ was analyzed. The filled epoxy composite not only compensates for this fragile property but enhances its dielectric strength.

• Tribology and Lubricants
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• 제27권1호
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• pp.25-33
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• 2011

Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.261-264
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• 2008

In this paper the experiments of breakdown characteristics $SF_6$ liquid ($LSF_6$) in model GIS(Gas Insulated Switchgear) were described. From the experiments results, The ability of $LSF_6$ insulation is higher than high-pressurized $SF_6$ gas. The breakdown characteristics of $LSF_6$ were produced by bubble formed evaporation of $LSF_6$ and bubble caused by high electric emission. It is considered in this paper that the results are fundamental data for electric insulation design of superconductor and cryogenic equipments machinery which will be studied and developed in the future.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.178-179
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• 2006

In this paper the experiments of breakdown characteristics SF6 liquid ($LSF_6$) in model GIS(Gas Insulated Switchgear) were described. From the experiments results, The ability of $LSF_6$ insulation is higher than high-pressurized SF6 gas. The breakdown characteristics of $LSF_6$ were produced by bubble formed evaporation of $LSF_6$ and bubble caused by high electric emission. It is considered in this paper that the results are fundamental data for electric insulation design of superconductor and cryogenic equipments machinery which will be studied and developed in the future.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2003년도 추계학술대회 논문집
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• pp.213-217
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• 2003

In this paper, we studied electric Insulation characteristics of synthetic Laminated Polypropylene Paper (LPP) in liquid nitrogen (L$N_2$) for the application to high temperature super-conducting (HTS) cable. And, we selected the insulation paper/L$N_2$composite insulation type for the electric insulation design of a HTS cable. Furthermore, we compared the breakdown characteristics of the butt gap and bended mini-model cable that comes into being in this kind of cryogenic insulation type. It is necessary to understand the winding parameter of insulation paper/L$N_2$composite insulation.

• 한국초전도ㆍ저온공학회논문지
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• 제19권3호
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• pp.8-12
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• 2017

If the part of the HTS magnet is exposed to the outside of the cryogenic coolant due to the fluctuation of the height of the cooling liquid or the vapor generation, the uncooled part becomes very unstable. In this paper, the unstable equilibrium temperature distribution of the uncooled part of a superconductor is obtained, and the maximum temperature and energy are calculated as a function of the uncooled length. Similar to the superconductor stability problem, the current sharing model was applied to derive the theoretical formula and calculated by numerical integration. We also applied a jump model, which assumes that joule heat is generated in all of the uncooled segment, and compares it with the current sharing model results. As a result of the analysis, the stable equilibrium state and the critical uncooled length in the jump model are not shown in the current sharing model. The stability of the conductors to external disturbances was discussed based on the obtained temperature distribution, maximum temperature, and energy.

• 한국초전도ㆍ저온공학회논문지
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• 제19권4호
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• pp.45-50
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• 2017

This paper presents a conceptual design and analysis for a 1-kW-class high-temperature superconducting rotating machine (HTSRM) rotor. The designed prototype is a small-scale integration system of a HTSRM and a HTS contactless rotary excitation device (CRED). Technically, CRED and HTSRM are connected in the same shaft, and it effectively charges the HTS coils of the rotor field winding by pumping fluxes via a non-contact method. HTS coils in rotor pole body and toroidal HTS wire in CRED rotor are cooled and operated by liquid nitrogen in cryogen tank located in inner-most of rotor. Therefore, it is crucial to securely maintain the thermal stability of cryogenic environment inside rotor. Especially, we critically consider not only on mechanical characteristics of the rotor but also on cryogenic thermal characteristics. In this paper, we conduct two main tasks covering optimizing a conceptual design and performing operational characteristics. First, rotor parameters are conceptually designed by analytical design codes. These parameters consider to mechanical and thermal performances such as mechanical strength, mechanical rigidity, and thermal heat losses of the rotor. Second, mechanical and thermal characteristics of rotor for 1-kW-class HTSRM are analyzed to verify the feasible operation conditions. Hence, three-dimensional finite element analysis (3D-FEA) method is used to perform these analyses in ANSYS-Workbench platform.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마연구회
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• pp.61-64
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• 2003

In the response to an increasing demand for electrical energy, much effort aimed to develop and commercialise HTS power equipments is going on around the world. For the development, it is necessary to establish the dielectric technology in $LN_2$. Hence many types of dielectric tests should be carried out to understand the dielectric phenomena at cryogenic temperature and to gather various dielectric data. Among the many types dielectric tests, the barrier effect were conducted with the simulated electrode after analysing the insulating configuration of the pancake coil type HTS transformer. The influence of a barrier on the dielectric strength was measured according to the size and the position of the barrier. It was shown that the effectiveness, the ratio of the breakdown voltage in presence of barrier to the voltage without barrier, is highest when the barrier is placed at the needle electrode side. And the barrier effect was not depend on the electrode array. The life time to breakdown with decreasing the applied voltage was increased remarkably having wide error band but the shape parameter in Weibull distribution was almost constant.

• 터널과지하공간
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• 제16권3호
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• pp.241-250
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• 2006

LNG지하저장 핵심기술 중 하나인 ice ring 형성을 열-수리 역학 해석을 통해 분석하였다. ice ring은 극저온물질의 누출에 대한 이차방벽 역할과 지하수의 저장공동 침투에 대한 일차방벽역할을 수행한다. 따라서 ice ring의 두께와 위치는 콘크리트와 PU foam 및 멤브레인으로 구성된 일차방호재의 무결성 유지에 있어서 핵심인자가 된다. 수치해석을 통해 이러한 ice ring의 위치와 두께를 추정하였으며 온도와 지하수위 결과를 계측치와 비교하였다. 수치해석결과는 PU foam 열전도도의 온도의존성과 지하수의 상변화를 고려한 경우 파일럿 공동에서 측정한 계측치와 잘 일치하였다. 본 논문에서 제시한 수치해석 기법은 실규모 저장시설의 설계에 있어서 ice ring 형성을 모델링하는 데에 바로 사용될 수 있을 것으로 판단된다.