• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.548-552
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• 2007

본 논문에서는 연료전지자동차의 저전압 배터리 충${\cdot}$방전을 위한 3상 양방향 DC-DC 컨버터를 제안한다. 제안한 3상 컨버터는 기존의 단상 컨버터에 비해 인터리빙 효과의 증대로 인한 입${\cdot}$출력 필터 사이즈 감소와 변압기의 이용률 증가로 인한 VA정격의 감소가 가능하며, 기존의 위상제어 방식의 3상 컨버터와 달리 입${\cdot}$출력전압이나 부하변동에 따른 무효 전류의 중가 문제가 없다. 또한 MOSFET 스위치를 사용하여 고전압 측에서는 비대칭 소프트 스위칭을 성취할 수 있고, 저전압 측에서는 동기정류 방식을 적용하여 도통손실을 감소시킬 수 있어 효율과 전력밀도를 더욱 향상 시킬 수 있다. 본 논문에서는 제안하는 3상 양방향 DC-DC 컨버터의 동작원리와 기존방식과의 비교분석을 수행하였으며 시뮬레이션을 통해 검증하였다.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.178-181
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• 2007

본 논문에서는 연료전지자동차의 저전압 배터리 충 방전을 위한 3상 양방향 DC-DC 컨버터를 제안한다. 제안한 3상 컨버터는 기존의 단상 컨버터에 비해 인터리빙 효과의 증대로 인한 입 출력 필터 사이즈 감소와 변압기의 이용률 증가로 인한 VA정격의 감소가 가능하다. 고전압 측에서는 비대칭 소프트 스위칭이 되고, 저전압 측에서는 동기정류 방식으로 도통손실을 감소시켜 높은 효율과 전력밀도를 가질 수 있다. 제안하는 3상 양방향 DC-DC 컨버터의 동작원리와 기존방식과의 비교 분석을 수행하였으며 시뮬레이션을 통해 타당성을 검증하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.4
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• pp.639-647
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• 2022

The use of flames is essential in cutting, bending, and welding steel during a ship's construction process. While acetylene fuel is commonly used in steel cutting and the manufacturing process in shipyards, the use of propane as an alternative fuel has recently been increasing, due to the lower risk of explosion and propane's relatively low calorific value. However, propane fuel has a relatively slow processing speed and high slag generation frequency, thereby resulting in poor quality. Propylene is another alternative fuel, which has an excellent calorific value. It is expected to gain wider use because of its potential to improve the quality, productivity, and efficiency of steel processing. In this study, the combustion characteristics of propane and propylene fuel during steel plate processing were analyzed and compared. The reduction of greenhouse gases and other harmful gases when using propylene flame was experimentally verified by analyzing the gases emitted during the process. Heat distribution and tensile tests were also performed to investigate the effects of heat input, according to processing fuel used, on the mechanical strength of the marine steel. The results showed that when propylene was used, the temperature was more evenly distributed than when propane fuel was used. Moreover, the mechanical tests showed that when using propylene, there was no decrease in tensile strength, but the strain showed a tendency to decrease. Based on the study results, it is recommended that propylene be used in steel processing and the cutting process in actual shipyards in the future. Additionally, more analysis and supplementary research should be conducted on problems that may occur.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.53-60
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• 2020

In liquid-fuel spray combustion, an experimental study was conducted to observe the effect of ultrasonic excitation on the ultrasonically-atomized liquid fuel flame by controlling pressure field through an ultrasonic standing wave. Flame of the ultrasonically-atomized kerosene aerosol was visualized by using a high speed camera, DSLR, and Schlieren photography. The amount of fuel consumed was obtained by a precise flow-rate measurement technique during combustion, through which the ratio of carrier gas (air) to fuel mass was able to be obtained, too. As a result, it could be found that the combustion reaction-rate of the liquid-fuel aerosol was increased by applying an ultrasonic standing wave to the secondary flame zone of the flame.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.8
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• pp.1035-1040
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• 2011

In this study, many researches have been carried out against Energy Efficiency Operational Indicator(EEOI) of existing ships under discussion by IMO. This research is examined the method for the polices about IMO's greenhouse gas reducing emissions among them, we were analyzed the EEOI for existing ships. we have analyzed the result about applying EEOI using the calculation method of the rate of fuel consumption for cargo quantities to the actual existing ships and raised the problem. Based on this research, we were presented the improved EEOI about the engine load using fuel consumption and applied the existing ships. As a result, we concluded that the improved EEOI can define a resonable rate of $CO_2$ emissions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.740-746
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• 2008

In this paper, robust structural design of the PEMFC stack gasket is pursued with Taguchi method by considering the noise factor in stack assembly. The study of noise problem in stacking is required to secure the safety and performance improvement of PEMFC stack. The design parameters in the Taguchi method are selected so that the structural responses are insensitive to the noise factors. In the gasket analysis, a Mooney-Rivlin strain energy function is used to consider hyperelasticity between load and displacement. By uni-axial and equi-biaxial tension tests of the gasket, the material properties are determined for the use in robust design of PEMFC gasket. The robust design of the PEMFC stack may provide structural reliability.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.71-73
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• 2007

본 논문에서는 새로운 연료전지용 3상 전류형 능동 클램프 DC-DC 컨버터를 제안한다. 전류형 컨버터 구조에 능동 클램프 회로를 채용하여 과도기에 발생하는 서지전압을 저감하였고 모든 스위치에서 영전압 스위칭을 하며, 그 장점으로 : 연속적인 입력전류, 전압 오버슈트 제거, 영전압 턴 온 스위칭, 고주파 변압기 1차/2차 측에 부가적인 스너버 회로의 필요성 제거, 소프트 스위칭에 의한 저속 다이오드 적용 등이 있다. 더구나 대용량 발전 시스템에 적합하도록 전류형 컨버터 구조와 3상 전력변환 회로를 결합하였다. 3상 전력변환 적용의 장점은 : 입력전류 및 출력전압 주파수의 3배 증가, 스위치에 흐르는 RMS 전류 저감, 필터소자 용량 및 부피 감소, 고주파 변압기 이용률 증가, 전력회로의 단순화에 따른 전체 사이즈 축소 및 신뢰성 향상 등이 있다. 제안하는 3상 전류형 능동 클램프 DC-DC 컨버터는 이러한 장점들 때문에 발전용 연료전지 시스템의 승압형 DC-DC 컨버터에 적합하며 대용량 태양전지 발전 시스템 및 배터리 충전기 등에도 적용할 수 있다. 새로운 3상 DC-DC 컨버터와 함께 3상 PWM 알고리즘을 제안하며, 시뮬레이션과 프로토타입 제작, 실험을 통하여 그 성능을 평가, 확인한다.

• Plant Journal
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• v.18 no.1
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• pp.43-49
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• 2022

In this study, the operational characteristics of the 7.48 MW fuel cell power plant consisting of 17 units of 440 kW Phosphoric Acid Fuel Cell (PAFC) in operation since its commercial operation in December 2017 were explained and the heat recovery process of the plat using Organic Rankine Cycle (ORC)was simulated. The fuel cell system performance improvement and economic assessment were analyzed by calculating the amount of heat recovery and electric power available when connecting a 125 kW XLT Model ORC for hot water heat sources with 105℃, 40.8 t/h. The result of the study shows that integrating the 125 kW ORC to PAFC power plant would improve generating efficiency by about 0.6% through annually 851,472 kWh of electricity produced by ORC, and fuel cell and ORC integrated systems were calculated to have a 0.35% higher Internal Return Ratio and more Net Present Value of 1,249 million KRW than not installing ORC despite installation costs.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.317-324
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• 2010

Metal-supported solid oxide fuel cells (SOFCs) have been developed to commercialize SOFCs. This new type of SOFC has high mechanical strength, but its mass transfer rate may be low due to the presence of a contact layer. In this study, the mass transfer characteristics of an anode-supported SOFC and a metal-supported SOFC are studied by performing numerical simulation. Governing equations, electrochemical reactions, and ceramic physical-property models are determined simultaneously; molecular diffusion and Knudsen diffusion are considered in mass transport analysis of porous media. The experimental results are compared with simulation data to validate the results of numerical simulation. The average current density of the metal-supported SOFC is 23% lower than that of the anode-supported SOFC. However, because of the presence of the contact layer, the metal-supported SOFC has a more uniform distribution than the anode-supported SOFC.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.6
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• pp.641-648
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• 2011

Off-gases emitted from the anode of a molten carbonate fuel cell (MCFC) at high temperatures for power generation are used as fuel in catalytic combustion. The heat generated in the catalytic combustor is utilized as the heat for the endothermic reaction required for steam reforming. Among the various operational conditions of the integrated reactor, we varied the inlet gas compositions of the catalytic combustor according to fuel utilization in the MCFC and the ratio of steam to carbon in the reformer. Subsequently, the thermal behaviors and reaction characteristics of the integrated reactor were investigated experimentally. The fundamental data from this experimental study will be useful for the design and fabrication of a more practical integrated reactor in the future.