• 대한조선학회 특별논문집
• /
• 대한조선학회 2005년도 특별논문집
• /
• pp.38-43
• /
• 2005

The present study is concerned with the numerical analysis of the sloshing impact pressure of the Liquefied Natural Gas (LNG) carriers in rough sea. The reliable predictions of the both random tank motions in irregular waves and violent fluid flow in the LNG tanks are required for practical sloshing analysis procedure of LNG carriers. The three-dimensional numerical model adopting SOLA-VOF scheme is used to predict violent free surface movements of LNG tank in irregular motions. For accurate input motion of tank, a three-dimensional panel method program called SSMP (Samsung Ship Motion Program) is applied for seakeeping analysis. Comparison studies of sloshing analysis are carried out for No.2 tank of 138K and 205K LNG carriers to verify the safety of the LNG containment system of the proposed 205K large LNG carrier.

• 대한조선학회논문집
• /
• 제58권4호
• /
• pp.262-270
• /
• 2021

Consumption of Liquefied Natural Gas (LNG) has increased due to environmental pollution; therefore, the need for LNG carriers can efficiently transport large quantities of LNG, is increased. In various types of LNG Cargo Containment System (CCS), Membrane-type MARK-III composed of composite materials is generally employed in the construction of an LNG carrier. Among composite materials in a Mark-III system, glass-fiber composites act as a secondary barrier to prevent the inner hull structure from leakage of LNG when the primary barrier is damaged. Nevertheless, several cases of damage to the secondary barriers have been reported and if damage occurs, LNG can flow into the inner hull structure, causing a brittle fracture. To prevent those problems, this study conducted the applicability assessment of composite material manufactured by bonding glass-fiber and aluminum with epoxy resin and increasing layer from three-ply (triplex) to five-ply (pentaplex). Tensile tests were performed in five temperature points (25, -20, -70, -120, and -170℃) considering temperature gradient in CCS. Scanning Electron Microscopy (SEM) and Coefficient of Thermal Expansion (CTE) analyses were carried out to evaluate the microstructure and thermos-mechanical properties of the pentaplex. The results showed epoxy resin and increasing layer number contributed to improving the mechanical properties over the whole temperature range.

• 한국구조물진단유지관리공학회 논문집
• /
• 제14권4호
• /
• pp.141-147
• /
• 2010

LNG 천연가스로서 저장과 운반이 용이한 액체로 변형이 가능하며, 청정연료로 각광받게 되어, 석유에너지의 의존도를 낮추고 에너지사용의 다변화를 위해 1986년 인도네시아로부터 처음 도입된 이래로 산업의 성장과 더불어 그 수요량이 지속적으로 증가하고 있다. LNG는 천연가스의 부피를 영하 약 $-162^{\circ}C(-260^{\circ}F)$까지 냉각시켜 1/600까지 줄일 수 있으므로, 저장 및 운반에 있어서 매우 효율적이다. 현대의 LNG 저장탱크는 철근 콘크리트 이중벽과 내부 니켈방호벽 및 벽사이의 효율이 높은 단열재로 구성된 완전 방호식이 적용되고 있다. 단열재는 극저온의 온도가 LNG 탱크 외벽으로 전달되는 것을 차단하며, 바닥슬래브, 외벽 및 상부에 설치된다. LNG 저장탱크의 단열재의 배치에 따라 콘크리트 외조에 작용하는 온도분포에 차이가 나므로, 본 연구에서는 기 건설된 완전 방호식 LNG 저장탱크 바닥판 단열재의 배치에 대해 검토하고, 이를 바탕으로 단열시스템 개선 방안을 제안하고자 한다.

• Journal of Ship and Ocean Technology
• /
• 제11권3호
• /
• pp.24-38
• /
• 2007

It is a very challenging work to design large Arctic LNG carrier, since LNG carrier requires high reliability for the structural safety and the environment of Arctic region is known to be very severe. Therefore, special attention should be paid for the verifying the structural safety of LNG career particularly with regard to LNG leakage. In this paper, the safety of the hull structure and cargo containment system of 208K MK $III^{TM}$ type LNG carriers with Arc4 is investigated based on the direct calculation of ice loads as well as wave loads. From the whole investigation, it is clear that the developed vessel - 208K MK $III^{TM}$ type LNG carrier with RMRS Ice class Arc4 - has enough strength and is safe to be operated in Arctic region.

• 대한조선학회논문집
• /
• 제45권6호
• /
• pp.726-734
• /
• 2008

While the structural safety assessment of Cargo Containment System(CCS) in membrane type LNG carriers has to be carried out in consideration of sloshing impact pressure, it is very difficult to figure out its dynamic response behaviors due to its very complex structural arrangements/materials and complicated phenomena of sloshing impact loading. For the development of its original technique, it is necessary to understand the characteristics of dynamic response behavior of CCS structure under sloshing impact pressure. In this study, for the exact understanding of dynamic response behavior of CCS structure in membrane Mark III type LNG carriers under sloshing impact pressure, its wet drop impact response analyses were carried out by using Fluid-Structure Interaction(FSI) analysis technique of LS-DYNA code, and were also validated through a series of wet drop experiments for the enhancement of more accurate shock response analysis technique. It might be thought that the structural response behaviors of impact response analysis, such as impact pressure impulses and resulted strain time histories, generally showed very good agreement with experimental ones with very appropriate use of FSI analysis technique of LS-DYNA code, finite element modeling and material properties of CCS structure, finite element modeling and equation of state(EOS) of fluid domain.

• 대한조선학회논문집
• /
• 제45권6호
• /
• pp.735-749
• /
• 2008

For the development of the original technique of structural safety assessment of Cargo Containment System(CCS) in membrane type LNG carriers, it is necessary to understand the characteristics of dynamic response behavior of CCS structure under sloshing impact pressure. In the previous study, the wet drop impact response analyses of CCS structure in membrane Mark III type LNG carriers were carried out by using Fluid-Structure Interaction(FSI) analysis technique of LS-DYNA code, and were also validated through a series of wet drop experiments for the enhancement of more accurate shock response analysis technique. In this study, the characteristics of structural shock response behaviors of CCS structure were sufficiently figured out by careful examinations of the effects of specimen weight, drop height, incident angle, corrugation and stiffness of inner hull on its shock response behaviors. The shock response analysis of upward shooting fluid to inner hull was performed, and the reason of faster strain response than shock pressure one was also figured out.

• 한국가스학회지
• /
• 제8권2호
• /
• pp.35-41
• /
• 2004

본 논문은 완전 밀폐방식의 LNG 저장탱크에서 $9\%$ 니켈강재로 제작된 내부탱크 바닥판의 응력과 변위량에 대한 거동특성을 제시하고 있다. 내부탱크에 LNG가 유입되면서 바닥판이 최대 유체정압을 받는 경우, 내부탱크의 바닥판에 걸리는 응력과 변위량 분포를 내부탱크 바닥판의 기울기, 환상판 두께와 길이의 설계함수로 고찰하였다. 계산 결과에 의하면, $140,000m^3$ 저장용량의 내부탱크에서 바닥판의 기울기는 100${\~}$200 : 1 정도로 최적화 설계를 하는 것이 응력특성 측면에서 우수하다. 또한, 내부탱크 환상판의 두께는 20mm 정도, 환상판의 길이는 3m 이상으로 설정하는 것이 저장탱크의 안정성을 확보할 수 있다.

• 대한조선학회논문집
• /
• 제58권4호
• /
• pp.206-213
• /
• 2021

Recently, although the size of the LNG Cargo Containment System (CCS) has been increasing, the secondary barrier is reported to remain unchanged, and the conventional Flexible Secondary Barrier (FSB) used in Mark-III type has been pointed out to be vulnerable to failure owing to thermal and cyclic loads. In this respect, a tensile test was carried out to verify the reinforcing effect of FSB using aramid fiber on weft compared to the conventional FSB. In order to consider the LNG leakage situation, a series of tensile tests were conducted from ambient to cryogenic temperature, and mechanical properties were evaluated for each fiber direction on account of anisotropy. Tensile behavior and fracture analyses were performed to confirm the mechanical properties of each material according to temperature. Tensile test results proved that replacing the aramid fiber instead of E-glass fiber used on weft is effective in enhancing the mechanical properties.

• 한국해양공학회지
• /
• 제36권4호
• /
• pp.217-231
• /
• 2022

Reinforced polyurethane foam (R-PUF), a material for liquefied natural gas cargo containment systems, is expected to have different mechanical properties depending on its stacking position of foaming as the glass fiber reinforcement of R-PUF sinks inside R-PUF under the influence of gravity. In addition, since R-PUF is not a homogeneous material, it is also expected that the coordinate direction within this material has a great correlation with the mechanical properties. So, this study was conducted to confirm this correlation with the one between the mechanical properties and the stacking position. In particular, in this study, R-PUF of 3 different densities (130, 170, and 210 kg/m³) was used, and tensile, compression, and shear tests of this material were performed under 5 temperatures. As a result of the tests, it was confirmed that the strength and modulus of elasticity of the material increased as the temperature decreased. Specifically, the strength and modulus of elasticity in the Z direction, which was the lamination direction, tended to be lower than those in the other directions. Finally, the strength and elastic modulus of different specimens of the material found at the bottom of their lamination compared to the specimens with these properties found at positions other than their lamination bottom were evaluated. Further analysis confirmed that as the temperature decreased, hardening of R-PUF occurred, indicating that the strength and modulus of elasticity increased. On the other hand, as the density of R-PUF increased, a sharp increase in strength and elastic modulus of R-PUF was observed.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2011년도 정기 학술대회
• /
• pp.527-530
• /
• 2011

전 세계적인 LNG 수요 증가에 따라 LNG 운반선의 대형화 및 극한 환경의 항로 선택이 불가피해지고 있다. 이러한 상황에서 LNG의 슬로싱 현상에 따른 화물창의 구조적 안정성 여부가 큰 이슈거리로 떠오르고 있다. 슬로싱 현상에 의한 구조 안전성을 평가하는 가장 이상적인 방법은 유체 영역과 탱크의 복합적인 상호 작용을 완벽하게 구현하는 것이다. 하지만 과도한 계산 시간과 결과의 정확성이 확보되지 못한 상황에서 LNG 운반선 화물창의 안전성 평가에 적용하기에는 문제가 있다. 많은 연구 단체에서는 불규칙적인 슬로싱 압력 신호를 삼각파 등의 형태로 이상화하여 구조해석에 적용하고 있지만 이 또한 유체의 압축성 및 비선형성을 고려하는데 한계를 드러내고 있다. 본 연구에서는 슬로싱 하중을 받는 구조의 안전성을 평가함에 있어 쌍방향(2-way) FSI(Fluid-Structure Interaction)의 과도한 해석 시간 및 수렴의 어려움을 보안하고 유체의 비선형성을 고려할 수 있는 단 방향(1-way) FSI 기법을 이용하는 절차를 제안하고자 한다.