• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.95.2-95.2
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• 2012

고온형 SOFC의 개발에 있어 스택의 신뢰성을 확보하는데 가장 중요한 핵심기술은 스택 구성요소 사이를 접합하는데 필요한 고온형 밀봉재의 개발이다. SOFC 스택에서의 밀봉재는 고체전해질과 접속자 사이에서 음극에 공급되는 연료가스와 양극에 공급되는 공기가 서로 혼합되는 것을 방지하는 역할은 물론 기계적으로 취약한 단전지의 보호 및 스택전체 구조물의 구조적 일체성(Structural integrity)을 부여하는데 주목적이 있다. 현재 기체 기밀성을 유지하기 위한 밀봉재는 크게 유리 및 결정화 유리계, mica및 mica/유리복합재료, 유리/충전재 복합재료 등이 사용되고 있으나 다수의 단위전지로 구성되는 스택 구성에서 스택의 열기계적 안정성 및 장기수명을 보장하기 위해서는 본 연구에서 개발하고자 하는 복합밀봉재가 가장 적합할 것으로 예상되고 있다. 본 연구에서는 SiO-B2O3-RO계에 BaO, SrO를 일정비율로 첨가하여 제작된 유리 frit을 열처리하여 물리화학적 물성변화를 검토하였으며, $750^{\circ}C$ 이하의 연화점을 갖는 유리를 기지상으로 하고 세라믹 보강재를 첨가한 고온형 복합밀봉재를 개발하고 그 물리화학적 안정성, 열기계적 안정성 및 밀봉 특성을 평가하였다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2021-2025
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• 2007

Performance of single cell at solid oxide fuel cell (SOFC) system is largely affected by electrocatalytic and thermal properties of cathode. Samarium-based perovskite oxide material is recently recognized as promising cathode material for intermediate temperature-operating SOFC due to its high electrocatalytic property. Perovskite structured $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$ and its composite material, $Sm_{0.5}Sr_{0.5}CoO_{3-\delta}/Sm_{0.2}Ce_{0.8}O_{1.9}$ were investigated in terms of area specific resistance (ASR), thermal expansion coefficient (TEC), thermal cycling and long term performance. $Sm_{0.2}Ce_{0.8}O_{1.9}$ was used as electrolyte material. Electrochemical ac impedance spectroscopy (EIS) and dilatometer were used to measure the cathodic properties. Composite cathode ($Sm_{0.5}Sr_{0.5}CoO_{3-\delta}$: $Sm_{0.2}Ce_{0.8}O_{1.9}$ = 6:4) showed a good ASR of 0.13${\Omega}$ $cm^2$ at 650$^{\circ}C$ and its TEC value was 12.3${\times}$10-6/K at 600$^{\circ}C$ which is similar to the value of ceria-based electrolyte of 11.9${\times}$10-6/K. Performance of composite cathode was maintained with no degradation even after 13 times thermal cycle test.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.83.2-83.2
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• 2010

평판형 고체산화물 연료전지(planar SOFC : Solid oxide Fuelcell)는 높은 전류 효율 및 출력밀도를 가지는 중,대형 발전용 전기소자이다. SOFC 스택을 600~800도에서 작동할 경우, 금속 분리판에서 휘발된 크롬에 의한 열화현상과 금속의 산화에 의한 표면 저항의 증가가 큰 문제점으로 알려져 있으며, 이를 개선하기 위한 많은 연구가 진행되고 있다. 본 연구에서는 금속 분리판의 열화를 억제하기 위한 여러 보호코팅의 특성을 밝히고, 특성차이의 원인을 분석하고자 하였다. 모재는 상용 STS444합금 (Nisshin steel 생산) 2.0mmt 박판을 사용하였으며, 표면 상태를 균일하게 하기 위하여 표면은 동일한 #1200 번 사포로 연마후 코팅하였다. 적용한 코팅은 전기도금 Ni 코팅, (MnCo)3O4 wet powder spray 코팅, (MnCo)3O4 ADM코팅 3종이었으며, 코팅층의 두께는 최적 공정조건에 따라 달리 하였다. 산화후 형성되는 표면 산화물의 전기적 특성을 평가하기 위하여 시험편의 비면적 저항 (ASR : area specific resistance)을 장시간 측정하였다. 측정편의 크기는 가로 4cm ${\times}$ 세로 4cm였으며, 100시간 공기중 산화후 측정하였다. 표면 접촉을 높이기 위하여 Pt paste를 40~50um도포하였으며, 1~0.1A인가된 전류에 대한 저항을 4전극법 (4-probe)으로 측정하였다. 표면 코팅층이 크롬 휘발을 억제하는 정도를 평가하기 위하여 크롬 휘발량을 측정하였다. 시편은 가로 1.5cm ${\times}$ 세로 1cm 였으며, 공급된 공기와 수분의 혼합가스와 응축기 표면에 흡착된 크롬의 양을 ICP-MASS법으로 측정하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.231-235
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• 2009

The mainly objectives of this study was a combustion dynamics and instability characteristics in a model dump type combustor which is scale down of GE 7FA+e DLN 2.6 gas turbine combustor with running at Seo-Inchon combined cycle power plant. Model gas turbine injector has 2-stage swirl vane and it's reduced 1/3 size of the original one. The shape of plenum and combustor were designed for similar acoustic characteristics. As the result, this research have been shows the peak frequency of model combustor was changed quarter-wave mode to Helmholtz resonator mode in plenum and longitudinal mode in dump combustor at unstable flame conditions caused by the different of combustor temperature and fuel-air mixture distributions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.21-27
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• 2015

In order to meet the current emission regulations (EURO-6), it is necessary to significantly reduce $CH_4$ and $NO_X$ emissions. This study investigated the effect of a reduction in the valve overlap on the combustion and emission characteristics of a hydrogen-compressed natural gas engine under a part-load operating condition. The combustion and emission characteristics were analyzed for each fuel using the original camshaft and an altered camshaft with reduced valve overlap. The results showed that the thermal efficiency was decreased and the fuel flow was increased when using the altered camshaft. The $CO_2$ and $CH_4$ emissions were increased as a result of the reduced thermal efficiency. Under lean operating conditions, the $NO_X$ emission was decreased compared with one of the conventional camshaft. Thus, under the same fuels and operating conditions, it had a harmful influence on the emission characteristics and thermal efficiency.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.3
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• pp.617-622
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• 2018

Simultaneous control of blowers and heat exchangers affecting the air sealing and flow conditions inside the green house is essential to the management of $CO_2$ concentration. Currently, the demand for automation systems and integrated control is steadily increasing according to increasing of farm areas per person due to the reduction of agricultural population. This paper proposes the integrated control system that can control simultaneously the existing devices such as measurement switching devices which are important variables in the supply of $CO_2$, $CO_2$ generator fuel and combustion air mixture ratio(air-to-fuel ratio), and $CO_2$ supply control under internal and external conditions.

• Plant Journal
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• v.7 no.2
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• pp.44-51
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• 2011

Given the fact that the entire bituminous coal used for a boiler is imported, the supply of coal is often affected by the rise of international coal price. Moreover, coal suppliers have been diversified due to the competition among power generation companies for reducing costs and inexpensive sub-bituminous coal is used. As a result, boilers combustion conditions have been deviated from the initial boiler design. This requires the selection of adequate excessive air ratio for different combustion conditions to enhance the efficiency of boiler operation. The boiler efficiency has been identified through an examination on the change of excessive air ratio by mixed fuel in unit 8 of Dangjin power plant complex. In addition, an excessive air ratio was calculated based on the examination result. According to the study result, the adequate excessive air ratio was 13% when Macquarie and Powder river were mixed at a ratio of 5:5 and when Sonoma and Megaprima persada were mixed at a ratio of 5:5. When BHP Billiton and Powder river were mixed at a ratio of 4:6 and Centennial and Batubara were mixed at a ratio of 3:7, the adequate excessive air ratio was 11%.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.250-256
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• 2013

Gasoline generates organic acid and polymer (gum) by hydrocarbon oxidation depending on the storage environment such as temperature and exposure to sunlight, which can cause metal corrosion, rubber and resin degradation and vehicle malfunction caused by accumulation in fuel supply system. The gasoline which has not been used for a long time in bi-fuel (LPG-Gasoline) vehicle causes problems, and low octane number gasoline have evaporated into the field, but the exact cause has not been studied yet. In this study, we suggest a plan of quality management by investigating the gasoline oxidation behavior. In order to investigate the oxidation behavior of gasoline, changes of gasoline properties were analyzed at various storage conditions such as storage time, storage vessel type (vehicle fuel tank, PE vessel and Fe vessel) and storage circumstances (sunlight exposure and open system, etc.). Currently distributing gasoline and bioethanol blended fuel (blended 10%) were stored for 18 weeks in summer season. The sample stored in PE vessel was out of quality standard (octane number, vapor pressure, etc.) due to the evaporation of the high octane number and low boiling point components through the vessel cap and surface. Especially, the sunlight exposure sample stored in PE vessel showed rapid decrease of vapor pressure and increase of gum. Bioethanol blended fuel showed similar results as gasoline.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.103-110
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• 2012

The flow field, fuel-air mixing, and behaviors of turbulent flames have been investigated using the large eddy simulation (LES) numerical technique in a premixed swirl combustor equipped with EV double cone burners. Recirculation zones are generated by the swirl burner, and lean premixed flames are formed within a distance of 0.2 m from the tip of the burner. NOx emission of 0.46 ppm is predicted at 1 atm and an air/fuel ratio of 38.7. However, most of the CO generated in a flame front continues to be oxidized as it moves toward the exit, and CO emission of 5.45 ppm is predicted at the exit. The NOx emission can be reduced by decreasing the pressure and air/fuel ratio. The characteristics of NOx emission have been investigated through RANS simulations for various fuel injection types, and it is found thereby that five-lance-hole injection produces the lowest NOx emission rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.9
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• pp.792-798
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• 2007

catalytic combustion is accomplished by the chemical reaction between fuel and oxidizer at the catalyst surface, different from conventional combustion. Therefore, it is important that the fuel and air stream are well mixed and supplied uniformly prior to the combustion region. If the flow is maldistributed, a hot spot may occur that can lead to subsequent catalyst and substrate damage. Therefore, in order to enhance the mixing and flow uniformity, in this study, the perforated plate is used. A numerical simulation is performed to investigate the variation of flow characteristics by changing various parameters. Under each condition, the uniformity of the flow stream at the entrance of the catalyst section is evaluated and compared. The results show that the uniformity can be effectively improved for most of the case by using the well-designed perforated plates.