• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.3
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• pp.352-359
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• 2018

As a fuel for ship propulsion, liquefied natural gas (LNG) is currently considered a proven and reasonable solution for meeting the IMO emission regulations, with gas engines for the LNG-fueled ship covering a broad range of power outputs. For an LNG-fueled ship, the LNG bunkering process is different from the HFO bunkering process, in the sense that the cryogenic liquid transfer generates a considerable amount of boil-off gas (BOG). This study investigated the effect of the temperature difference on boil-off gas (BOG) production during ship-to-ship (STS) LNG bunkering to the receiving tank of the LNG-fueled ship. A concept design was resumed for the cargo/fuel tanks in the LNG bunkering vessel and the receiving vessel, as well as for LNG handling systems. Subsequently, the storage tank capacities of the LNG were $4,500m^3$ for the bunkering vessel and $700m^3$ for the receiving vessel. Process dynamic simulations by Aspen HYSYS were performed under several bunkering scenarios, which demonstrated that the boil-off gas and resulting pressure buildup in the receiving vessel were mainly determined by the temperature difference between bunkering and the receiving tank, pressure of the receiving tank, and amount of remaining LNG.

• Journal of Power System Engineering
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• v.21 no.4
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• pp.70-76
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• 2017

This paper presents the development of a Gas Valve Train (GVT) control system which is the core equipment of LNG fueled vessels. Due to the increasing worldwide demand for echo friendly green ship products, domestic companies urgently require to develop a core equipments for the LNG fueled vessels to secure worldwide markets in marine engineering. A LNG fueled engine generally equips the GVT, a fuel supply system that steadily supplies clean high-pressure LNG to the engine. The GVT requires a safety operational control system that can prevent any gas leakage accident, and a system that monitors operation status in real time. Therefore, we introduces a development for GVT control and monitoring system design and the design was systematically performed by means of functional analysis and differentiation of foreign advanced products.

• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.9-13
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• 2015

While environmental concern is urging shipbuilding industry to reduce pollutant emission, it is necessary to design environmental friendly vessels. LNG as fuel for ship propulsion is proven to be effective way to reduce pollutant emission. In this study, we find optimum position of LNG fuel supply system on AHTS by considering vessel characteristic. Three different positions of fuel supply system are studied in this paper. Factors such as stability, strength and safety are examined in each position of fuel supply system.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.5
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• pp.447-452
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• 2016

The use of gas as fuel, particularly liquefied natural gas (LNG), has increased in recent years owing to its lower sulfur and particulate emissions compared to fuel oil or marine diesel oil. LNG is a low temperature, volatile fuel with very low flash point. The major challenges of using LNG are related to fuel bunkering, storing, and handling during ship operation. The main components of an LNG fuel system are the bunkering equipment, fuel tanks, vaporizers/heaters, pressure build-up units (PBUs), and gas controlling units. Low-pressure dual-fuel (DF) engines are predominant in small LNG-powered vessels and have been operating in many small- and medium-sized ferries or LNG-fueled generators.(Tamura, K., 2010; Esoy, V., 2011[1][2]) Small ships sailing at coast or offshore rarely have continuous operation at constant engine load in contrast to large ships sailing in the ocean. This is because ship operators need to change the engine load frequently due to various obstacles and narrow channels. Therefore, controlling the overall system performance of a gas supply system during transient operations and decision of bunkering time under a very poor infrastructure condition is crucial. In this study, we analyzed the fuel consumption, the system stability, and the dynamic characteristics in supplying fuel gas for operating conditions with frequent engine load changes using a commercial analysis program. For the model ship, we selected the 'Econuri', Asia's first LNG-powered vessel, which is now in operation at Incheon Port of South Korea.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.181-181
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• 2017

• Journal of the Society of Naval Architects of Korea
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• v.54 no.1
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• pp.1-9
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• 2017

LNG has significant advantages in regard to environmental aspects comparing with conventional fuel oil. In fact, it is estimated that NOx and SOx emission can be reduced by about 90% and 100%, respectively in case of using LNG as a fuel. LNG-fuelled ship has been considered to be the best option both from an environmental and an economic point of view. Along with these trends, some major shipyards and Classification Societies have started to carry out the risk-based system design for LNG-fuelled ship such as passenger ship, platform supply vessel and large container vessel etc. However, new conceptual gas fuelled ship has high risk level compared with vessel using traditional crude oil especially in view of gas explosion accident. Therefore safety area where installed fuel gas supply system is required risk based system design with special considerations. On this paper, the entire process necessary for the quantitative risk analysis was explained to meet the satisfactory safety level of gas fuelled ship.

• Journal of Ocean Engineering and Technology
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• v.34 no.1
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• pp.19-25
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• 2020

This paper proposes the optimal shape of an LNG fuel tank with a lattice pressure vessel (LPV) design for a tugboat. The LPV is a Type C tank with a design philosophy of "design by analysis," which facilitates greater variability of shape compared with other traditional Type C tanks. Further, compared with conventional cylindrical fuel tanks, the LPV provides better volumetric efficiency. Considering the shape of a fuel tank room, a trapezoidal shape of the LPV is concluded as the most optimal design. This study performs two major analyses of the LPV: structural and heat transfer analyses. First, a design procedure of the LPV based on structural analyses is elaborated. The finite element method is used for the analyses. Furthermore, the results guarantee that the maximum stresses by applied loads do not exceed an allowable stress limitation. Second, the heat transfer analysis of the LPV is conducted. LNG boil-off gas generation is analyzed based on various insulation materials and the degree of acuum.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.174-179
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• 2016

To protect the ocean environment, the use of liquefied natural gas (LNG) carriers, bunkering ships, and fueled ships is increasing. Recently, Korean shipbuilders have developed and supplied a partial reliquefaction facility for boil-off-gas (BOG). Despite reasonable insulation, heat leakage in vessel storage tanks causes LNG to be continuously evaporated as BOG. This research analyzed the maximum liquid yield rate for various partial reliquefaction systems (PRS) and considered related factors affecting yields. The results showed a liquid yield of 48.7% from an indirect PRS system (heat exchanges between cold flash gas and compressed natural gas), and 41% from a direct PRS system (BOG is mixed with flash gas and discharged from a liquid-vapor separator). The primary factor affecting liquid yield was heat exchanger effectiveness; the exchanger's efficiency and insulation characteristics directly affect the performance of BOG reliquefaction systems.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.37-44
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• 2018

As the international Maritime Organization is tightening up the emission regulation vessel, many countries and companies are pushing ahead the LNG fuel as one of long term solution for emission problems of ship. as a study on the way to conduct business for LNG bunkering around the world, this study was analyzed in view-point of business models focused on major countries such as Japan, China, Singapore, Europe and United States. The results of this study are as follows. China first established a nation-centered LNG bunkering policy. And then, the state and the energy company have been cooperating and carrying on LNG bunkering business for LNG fueled ships. Some countries in Europe and United States are in the process of LNG bunkering business mainly with private company. To obtain cheaper LNG fuel than bunker-C, the private company has a business model of LNG bunkering on their own LNG fueled ships, while securing LNG with high price competitiveness through partnership with middle class operators such us LNG terminal and natural gas liquefaction plant. Also, the LNG bunkering business around the world is focused on private companies rather than public corporations, but it was going to be focused on large energy companies because the initial cost required to build LNG bunkering infrastructure. Three models (TOTE model, Shell model, ENGIE model) of LNG bun kering business are currently being developed. It has been found that the way in which LNG bunkering business is implemented by different countries is applied differently according to the enterprise and national policy.

• Special Issue of the Society of Naval Architects of Korea
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• 2017.10a
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• pp.93-104
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• 2017

IMO type C independent tank is one of the cargo containment system specified on IGC code. It is normally adopted for small and medium size liquefied gas carrier's cargo containment system and it can be applied to fuel tank of LNG fueled vessel. This study focuses on rule scantling process and evaluation methods in early design stage of type C independent tank. Actual design results of 22K LPG/Ammonia/VCM carrier's No.2 cargo tank are demonstrated. This paper presents the calculation methods of design acceleration and liquid height for internal design pressure as defined on IGC code. And this paper shows the applied results of classification rules about shell thickness requirement and buckling strength. Additionally this paper deals with evaluation methods of structural strength and cumulative fatigue damage using FE analysis.