• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.339-347
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• 2022

The post chamber in hybrid rocket is installed to induce additional increase in combustion enthalpy by allowing continuous burning of the liquefied fuels. When paraffin wax fuel is used, unsteady pressure oscillations are observed only at the beginning of combustion. This study intends to investigate the effect of additional combustion of liquefied fuel droplets on the occurrence of unsteady pressure fluctuations. For this, the combustion in post-chamber was visualized and image analysis using POD(Proper Orthogonal Decomposition) technique was performed. In addition, the hypothesis was proposed on the occurrence of unsteady pressure oscillations by identifying the modes including the behavior of droplets through mode reconstruction. Conducting a series of combustion tests, the amount of liquefied fuel flowing into the post chamber and the generation of fuel droplets were controlled. Also, the changes in frequency characteristic of unsteady pressure oscillation were monitored. As a result, the unsteady pressure oscillations observed in paraffin wax combustion were the result of additional combustion of fuel droplets generated in the post chamber.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.8-16
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• 2024

Because hydrogen has very low density, a different storage method is required to store the same amount of energy as fossil fuel. One way to increase the density of hydrogen is through liquefaction. However, since the liquefied temperature of hydrogen is extremely low at -252 ℃, it is easily vaporized by external heat input. When liquid hydrogen is vaporized, a self-pressurizing phenomenon occurs in which the pressure inside the hydrogen tank increases, so when designing the tank, this rising pressure must be carefully predicted. Therefore, in this paper, the internal pressure of a cryogenic liquid fuel tank was predicted according to the liquid hydrogen filling ratio. A one-dimensional thermodynamic model was applied to predict the pressure rise inside the tank. The thermodynamic model considered heat transfer, vaporization of liquid hydrogen, and fuel discharging. Finally, it was confirmed that there was a significant difference in pressure behavior and maximum rise pressure depending on the filling ratio of liquid hydrogen in the fuel tank.

• Journal of Navigation and Port Research
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• v.33 no.10
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• pp.659-664
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• 2009

LNG carriers have, up to 2006, mainly been driven by steam turbines. The Boil-Off Gas from the LNG cargo tanks has so far been used as fuel. This is a costly solution that requires special skills during construction and operation. Alternative propulsion systems offer far better fuel economical efficiency than steam turbines. Instead of previous practice using Boil-Off Gas as a fuel, the Re-liquefaction system establishes a solution to liquefy the Boil-Off Gas and return the LNG to the cargo tanks. This Re-liquefaction of Boil-Off Gases on LNG carriers results in increased cargo deliveries and allows owners and operators to choose the most optimum propulsion system. In this study, thermodynamic cycle analysis has been performed on two type of LNG Re-liquefaction system which was designed and adopted for the Q-Flex(216,000$m^3$) and Q-Max(266,000$m^3$) LNG carrier under construction at Korea ship yards and variable key factor was simulated to compare efficiency, power and nitrogen consumption of each Re-liquefaction system.

• Journal of the Korean Institute of Gas
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• v.17 no.3
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• pp.27-32
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• 2013

Natural gas liquefaction process which is operated under cryogenic condition spends large amount of energy. Most of energy in the natural gas liquefaction process is consumed by compressors. Therefore, minimizing energy consumption of compressors is an important issue in process design and operation. Among various natural gas liquefaction processes, propane pre-cooled mixed refrigerant (C3MR) process consists of mixed refrigerant system and pure refrigerant system. In this study, to find the optimal design of pure refrigerant system, pure refrigerant cycle is simulated on different number of pressure levels and the necessary energy of each design is compared. After that, the driver selection model is applied to analyse each processes, which has different number of equipments, in terms of cost. As the result, the design using many equipments spends lower energy. Using this result, this study suggests standard of process design selection by the cost term.

• Journal of the Korean Institute of Gas
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• v.4 no.2 s.10
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• pp.7-14
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• 2000

LNG (Liquified Natural Gas) carried by LNG ship is unloaded into the LNG storage tanks at the very low temperature (a little lower than the boiling point of LNG). Because LNG is unloaded through the pipeline, two phase flow appears in the pipeline. In this study, we have studied the pressure-drop mechanisms of the two-phase flow in the pipeline, and the calculation method of BOG (Boil-off Gas) amount based on the heat transfer mechanism through the insulation and the surface of the pipeline. We have developed a computer program for thermal-hydraulic analysis on the LNG pipeline system. We have also developed the optimal design program to find the optimal thickness of insulation and the pipeline size. The program searches the optimal design with the minimum capital cost of pipelines and insulation on the operating conditions of maximum allowance pressure-drop and BOG amount, etc.

• Environmental and Resource Economics Review
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• v.31 no.4
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• pp.711-731
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• 2022

In Korea, nuclear power plants are major sources of electricity supply with relatively low costs. Despite the importance and scale of nuclear electricity generation, the Korean tax and levy system is less organized than those in other countries, such as France and Japan, where nuclear power plants also play significant roles for electricity supply. Countries impose tax on nuclear electricity generation roughly in three ways: tax on nuclear reactors; tax on uranium fuel; tax on electricity from nuclear power plants. The Korean government may consider taxing nuclear electricity generation based on uranium fuel or electricity generation. If taxing on uranium fuel at the rate of 90 KRW per milligram of uranium, the Korean government can collect additional tax revenue of 430 billion KRW. If taxing on electricity from nuclear power plants at the rate of 11 KRW per kilowatt-hour, the government can collect additional tax revenue of 1,600 billion KRW.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.497-502
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• 2018

In Korea, passenger car and van using LPG fuel including taxi constantly increased due to the high cost of fuel. Recently, the emission standard has continuously tightened in the world. In this investigation was conducted the greenhouse gas emission characteristics of LPG vehicles according to the displacement and weight. Exhaust emission characteristics of 13 test LPG vehicles from about 1.0 L to 3.0 L displacements were measured and analyzed by using chassis dynamometer and emission analyzer. It is revealed that the greenhouse gas emission was showed the increasing tendency as the displacement and curb weight increased. Also, greenhouse gas emission of SC03 driving cycle has highest value and that of HWFET driving cycle shows the lowest value.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1192-1200
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• 2008

This paper is concerned with the thermal design of the $138,000m^3$ class membrane type LNGC. To predict the temperature distribution, BOG and BOR, 3-dimensional numerical calculation was carried-out for the quarter of No.3 LNG tank. These sequence analyses were performed under the standard conditions of IMO ship design condition, USCG ship design condition and the Korean flag LNGC's route condition according to the 6-voyage modes. As the results, temperature behavior, heat flux, total penetrating heat, BOG and BOR were obtained, and those were compared with the maneuvering results considering the real temperature variation of air and sea water temperature at noon time. For securing the safety of LNGC during the ballast voyage, optimum control patterns of pressure and temperature in LNG tank is suggested in this paper.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1999.07a
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• pp.313-319
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• 1999

간접열식 LPG온풍난방기는 LP(Liquefied Petroleum)가스를 열원으로 한 온풍난방기를 말한다. LP가스는 프로판(Propane, $C_3$H$_{8}$)과 부탄(Butane, $C_4$H$_{10}$)을 주성분으로 하는 혼합물로 에탄, 프로필렌, 부틸렌 등이 약간 포함되어 있는 기체로 액화 및 기화가 쉬우며 기체상태에서는 비중이 공기보다 무겁고 액체상태에서는 물보다 가볍다. 또한, 기화할 때는 다량의 열과 연소시 많은 공기를 필요로 하고 온도에 따라 액체의 부피가 변하는 특성을 가지고 있으며 무색, 무취, 무독하다. LP가스의 발열량은 12,000kcal/kg으로 경유나 보일러등유 보다 약 30% 정도 높아 난방연료로서의 사용 및 취급성이 우수하다. (중략)

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.1
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• pp.28-35
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• 2005

Fuel injection rate of an injector is affected by various injection conditions such as injection duration, fuel temperature, injection pressure, and voltage in LPG liquid injection systems for either a port-fuel-injection(PFI) or a direct injection(DI) in a cylinder. Even fuel injection conditions are changed, the air-fuel ratio should be accurately controlled to educe exhaust emissions. In this study, correction factor for the fuel injection rate of an injector is derived from the density ratio and the pressure difference ratio. A voltage correction factor is researched from injection test results on an LPG liquid injection engine. A compensation method of the fuel injection rate is proposed for a fuel injection control system. The experimental results for the LPG liquid injection system in a SI-engine show that this system works well on experimental range of engine speed and load conditions. And the fuel injection rate is accurately controlled by the proposed compensation method.