• 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.

• Journal of ILASS-Korea
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• v.19 no.1
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• pp.1-8
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• 2014

Liquefied petroleum gas (LPG) is regarded as an alternative fuel for spark ignition engine due to similar or even higher octane number. In addition, LPG has better fuel characteristics including high vaporization characteristic and low carbon/hydrogen ratio leading to a reduction in carbon dioxide emission. Recently, development of LPG direct injection system started to improve performance of vehicles fuelled with LPG. However, spray characteristics of LPG were not well understood, which is should be known to develop injector for LPG direct injection engines. In this study, effects of operation condition including ambient pressure, temperature, and injection pressure on spray properties of n-butane were evaluated and compared to gasoline in a multi-hole injector. As general characteristics of both fuels, spray penetration becomes smaller with an increase of ambient pressure as well as a reduction in the injection pressure. However, it is found that evaporation of n-butane was faster compared to gasoline under all experimental condition. As a result, spray penetration of n-butane was shorter than that of gasoline. This result was due to higher vapor pressure and lower boiling point of n-butane. On the other hand, spray angle of both fuels do not vary much except under high ambient temperature conditions. Furthermore, spray shape of n-butane spray becomes completely different from that of gasoline at high ambient temperature conditions due to flash boiling of n-butane.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.617-623
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• 2008

GTL (gas-to-liquid) fuel produced by the Fischer-Tropsch reaction of carbon monoxide (CO) and hydrogen ($H_2$) is expected to be one of the environmental friendly biomass based alternatives and blended to petrodiesel. In this study, the characteristic of the fuel was analyzed by its concentration differences after blending petrodiesel in domestic market with different amounts of GTL fuel which produced from Shell. Gas chromatography shows that GTL fuel consists of longer paraffin chain than common diesel. GTL fuel showed a high flash point, distillation, kinematic viscosity, and derived cetane number. In addition, GTL fuel showed lower lubricity due to low sulfur content.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.1-6
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• 2008

For the safety design and operation of many gas process, it is necessary to know certain explosion limit, flash point, autoignition temperature (AIT) and minimum oxygen concentration of handling substances. Also it is necessary to know explosion limit at high temperature and pressure. In this study for the safe handling of hydrogen, explosion limit and AIT of combustion properties for hydrogen were investigated. By using the literatures data, the lower and upper explosion limits of hydrogen recommended 4.0 vol% and 77.0 vol%. Also the AIT of hydrogen with ignition sources recommended $400^{\circ}C$ at the electrically heated crucible furnace (the whole surface heating) and recommended $640^{\circ}C$ at the local hot surface. The new equations for predicting the temperature and the pressure dependence of the explosion limits of hydrogen are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Korean Journal of Materials Research
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• v.34 no.5
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• pp.223-234
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• 2024

This review explores the potential of pillared bentonite materials as solid acid catalysts for synthesizing diethyl ether, a promising renewable energy source. Diethyl ether offers numerous environmental benefits over fossil fuels, such as lower emissions of nitrogen oxides (NO_x) and carbon oxides (CO_x) gases and enhanced fuel properties, like high volatility and low flash point. Generally, the synthesis of diethyl ether employs homogeneous acid catalysts, which pose environmental impacts and operational challenges. This review discusses bentonite, a naturally occurring alumina silicate, as a heterogeneous acid catalyst due to its significant cation exchange capacity, porosity, and ability to undergo modifications such as pillarization. Pillarization involves intercalating polyhydroxy cations into the bentonite structure, enhancing surface area, acidity, and thermal stability. Despite the potential advantages, challenges remain in optimizing the yield and selectivity of diethyl ether production using pillared bentonite. The review highlights the need for further research using various metal oxides in the pillarization process to enhance surface properties and acidity characteristics, thereby improving the catalytic performance of bentonite for the synthesis of diethyl ether. This development could lead to more efficient, environmentally friendly synthesis processes, aligning with sustainable energy goals.

• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.1
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• pp.33-42
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• 2014

Purpose: I-131 scan using High Energy (HE) collimator is generally used. While, Medium Energy (ME) collimator is not suggested to use in result of an excessive septal penetration effects, it is used to improve the sensitivities of count rate on lower dose of I-131. This research aims to evaluate I-131 SPECT/CT image quality using by HE and ME collimator and also find out the possibility of ME collimator clinical application. Materials and Methods: ME and HE collimator are substituted as Siemens symbia T16 SPECT/CT, using I-131 point source and NEMA NU-2 IQ phantom. Single Energy Window (SEW) and Triple Energy Windows (TEW) are applied for image acquisition and images with CTAC and Scatter correction application or not, applied different number of iteration and sub set are reconstructed by IR method, flash 3D. By analysis of acquired image, the comparison on sensitivities, contrast, noise and aspect ratio of two collimators are able to be evaluated. Results: ME Collimator is ahead of HE collimator in terms of sensitivity (ME collimator: 188.18 cps/MBq, HE collimator: 46.31 cps/MBq). For contrast, reconstruction image used by HE collimator with TEW, 16 subset 8 iteration applied CTAC is shown the highest contrast (TCQI=190.64). In same condition, ME collimator has lower contrast than HE collimator (TCQI=66.05). The lowest aspect ratio for ME collimator and HE collimator are 1.065 with SEW, CTAC (+) and 1.024 with TEW, CTAC (+) respectively. Conclusion: Selecting a proper collimator is important factor for image quality. This research finding tells that HE collimator, which is generally used for I-131 scan emitted high energy ${\gamma}$-ray is the most recommendable collimator for image quality. However, ME collimator is also applicable in condition of lower dose, lower sensitive if utilizing energy window, matrix size, IR parameter, CTAC and scatter correction appropriately.