• 한국자동차공학회논문집
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• 제16권2호
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• pp.158-165
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• 2008

The combustion and exhaust emissions characteristics of a liquefied petroleum gas-di-methyl ether compression ignition engine with a variable valve timing device were investigated under various liquefied petroleum gas injection timing conditions. Liquefied petroleum gas was used as the main fuel and was injected directly into the combustion chamber. Di-methyl ether was used as an ignition promoter and was injected into the intake port. Different liquefied petroleum gas injection timings were tested to verify the effects of the mixture homogeneity on the combustion and exhaust emission characteristics of the liquefied petroleum gas-di-methyl ether compression ignition engine. The average charge temperature was calculated to analyze the emission formation. The ringing intensity was used for analysis of knock characteristics. The combustion and exhaust emission characteristics differed significantly depending on the liquefied petroleum gas injection and intake valve open timings. The CO emission increased as the intake valve open and liquefied petroleum gas injection timings were retarded. However, the particulate matter emission decreased and the nitrogen oxide emission increased as the intake valve open timing was retarded in the diffusion combustion regime. Finally, the combustion efficiency decreased as the intake valve open and liquefied petroleum gas injection timings were retarded.

• 한국항공우주학회지
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• 제35권4호
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• pp.323-328
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• 2007

소형 인공위성의 전형적인 추진 시스템인 냉가스 추진 시스템에 액화 연료를 직접 적용하여 성능을 분석하였다. 고려하는 액화 연료 냉가스 추진 시스템과 일반적으로 사용되는 질소 추진 시스템의 성능을 비교하였다. 질소 추진 시스템과 동일한 질량 조건, 동일한 부피 조건, 동일한 총 임펄스 조건에서 각각 액화 연료를 사용한 냉가스 시스템의 성능과 필요한 연료 탱크의 부피, 필요한 추진 시스템의 질량을 산출하였다. 액화 연료를 사용한 냉가스 추진 시스템은 일반적인 질소 추진제를 사용한 시스템보다 성능, 부피 및 질량 등에서 많은 이점을 가지며 냉가스 추진 시스템에 직접적으로 적용이 가능함을 알 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.148-154
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• 2004

As a rocket propellent of hydrocarbon fuels, the characteristics of liquefied natural gas was evaluated with the viewpoint of the constituents and content, the cooling performance as a coolant, and characteristic velocity and specific impulse as parameters of the engine performance. Content of methane was a principal factor to determine the characteristics as a rocket propellant and more than 90 % of it was needed as a fuel and coolant in the regenerative cooled liquid rocket engine. Some constituents of the liquefied natural gas can be frozen by the pre-cooling of the pipe lines, therefore they can be a factor disturbing the normal working of engine. In case the content of methane is around 90% in the liquefied natural gas, a normalized stoichiometric O/F mixture ratio of 0.75 is suggested for a nominal operation condition to get the maximum specific impulse and characteristic velocity.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2211-2216
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• 2007

Liquefied gas vaporizer means machine to vaporize the liquefied gas as liquid nitrogen($LN_2$), liquefied natural gas(LNG), liquid oxygen($LO_2$) etc. In the air type vaporizer, the frozen dew is also created by temperature drop (below 273 K) on vaporizer surface. This problem increases as the time progresses and humidity increases. In addition, the frozen dew gradually becomes frost deposit consequently, heat transfer through vaporizer decreases because frost deposit form adiabatic sheet. Because of this reason, recent vaporizer system is installed as parallel type, this vaporizer system needs more expensive installation costs and more space. This paper was investigated on the heat transfer characteristics of liquefied gas vaporizer with super low temperature and this paper was carried out the numerical about air heating vaporizer with super low temperature. The numerical analysis on the heat transfer was studied on the effect of geometric parameters of the vaporizer, which are length 1000 mm of 4fin75le type vaporizer. 4fin75le means number of fin is 4 and height of fin is 75 mm.

• 동력기계공학회지
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• 제11권1호
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• pp.56-62
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• 2007

This paper represents the cold energy for liquefied nitrogen gas and cascade refrigerator. In this study, the vaporizer of liquefied nitrogen gas has the fin coil tube type with the dimension of inside diameter of 10mm and outside diameter of 12mm. Also, the total length of vaporizer is 20,000mm. The main experimental parameters are the mean velocity in duct and the supplied flow-rates of liquefied nitrogen gas. For the cascade refrigeration system, the refrigerants are ethane(R 170) in the high pressure stage and R 22 in the low pressure stage.

• Journal of Advanced Marine Engineering and Technology
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• 제39권10호
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• pp.1037-1043
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• 2015

In recent years, Floating Liquefied Natural Gas (FLNG) Unit have attracted considerable attention. Generally, liquefied natural gas (LNG) units are produced in onshore liquefaction terminals from gas supplied from onshore gas fields or large-scale offshore gas fields near the coast. However, the development of these gas fields has approached saturation. Large-scale offshore gas fields far from the coast, as well as undeveloped medium- and small-scale offshore gas fields, have recently attracted attention. Among several proposed concepts, the floating LNG plant in the form of the FLNG system was chosen for further evaluation and development, considering worldwide receiving infrastructure. The design of a 2.5 million tonne per annum FLNG unit has been completed with a capacity corresponding to that of modern onshore liquefaction plants. Various simulation tests were performed to evaluate the performance of the electrical power plant, focusing on the efficiency of the electrical system to secure the aspects of plant safety. This design study analyzes the electrical system for the FLNG unit to improve the safety of operation and maintenance in the field.

• Advances in Energy Research
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• 제3권1호
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• pp.31-43
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• 2015

This paper compares the performance of JP-8(Jet Propellant) fuel and liquefied petroleum gas (LPG) and natural gas in the F110 GE100 jet engine. The cost of natural gas usage in gas turbine engines is lower than JP-8 and LPG. LPG cost is more than JP-8. LPG volume is bigger than JP-8 in the same flight conditions. Fuel tank should be cryogenic for using natural gas in the aircraft. Cost and weight of the cryogenic tanks are bigger. Cryogenic tanks decrease the move capability of the aircraft. The use of jet propellant (JP) is the best in available application for F110 GE 100 jet engine.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.383-384
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• 2022

Gas Combustion Unit (GCU) onboard liquefied natural gas carriers handles boil-off to stabilize tank pressure. There are many factors for LNG cargo operators to take into consideration to determine whether to use GCU or not. Gas consumption of main engine and re-liquefied gas through the Partial Re-Liquefaction System (PRS) are good examples of these factors. Human gas operators have decided the operation so far. In this paper, some deep learning neural network models were developed to provide human gas operators with a decision support system. The models consider various factors specially into GCU operation. A deep learning model with Sigmoid activation functions in input layer and hidden layers made the best performance among eight different deep learning models.

• 동력기계공학회지
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• 제11권3호
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• pp.22-28
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• 2007

Liquefied gas vaporizer is a machine to vaporize liquefied gas such as liquid nitrogen($LN_{2}$), liquefied natural gas(LNG), liquid oxygen($LO_{2}$) etc. For the air type vaporizer, the frozen dew is created by temperature drop (below 273 K) on vaporizer surface. The layer of ice make a contractions on vaporizer. The structure analysis on the heat transfer was studied to see the effect of geometric parameters of the vaporizer, which are length 1000 mm of various type vaporizer. Structure analysis result such as temperature variation, thermal stress and thermal strain have high efficiency of heat emission as increase of thermal conductivity. As the result, Frist, With-fin model shows high temperature distribution better than without-fin on the temperature analysis. Second, Without-fin model shows double contractions better then with-fin model under the super low temperature load on the thermal strain analysis. Third, Vaporizer fin can be apply not only heat exchange but also a stiffener of structure. Finally, we confirm that All model vaporizer can be stand for sudden load change because of compressive yield stress shows within 280 MPa on thermal stress analysis.

• 한국가스학회지
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• 제19권5호
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• pp.98-103
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• 2015

현행 액화석유가스의 안전관리 및 사업법의 시행규칙에 의거하면 액화 가스는 용기 체적의 85%까지 충전하도록 되어있다. 이에 상당하는 충전량은 $65^{\circ}C$를 기준으로 내부에 액체의 열팽창을 고려한 수치이다. 하지만 소형 또는 이동이 용이한 용기가 특정 상황에서는 용기 내부 액체의 온도가 $65^{\circ}C$ 미만을 유지한다고 단정 지을 수 없다. 열역학적 관점에서 액 팽창은 용기 재료의 강성만으로 제어하기 어려운 요소이며, 결국 파열 등의 사고를 유발 할 수 있는 잠재적인 위험 요인이 된다. 따라서 본 논문에서는 밀폐계에서 임계상태 액체 프로판의 열 팽창량을 추정하는 방법과 추정 된 결과를 제시 할 것이며, 내압 변화에 따른 용기의 체적 증가를 유도하는 구조적 요소를 실험적으로 제안할 것이다. 본 논문을 통해 제시된 결과는 향후 액화가스의 압력용기 설계에 있어 중요한 기초 자료가 될 것으로 사료된다.