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전기저항형 금속산화물 센서의 인쇄공정 최적화에 관한 연구
이석환,구지은,이문진,정정열,장지호,Lee, Seokhwan,Koo, Jieun,Lee, Moonjin,Jung, Jung-Yeul,Chang, Jiho 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.6
In this paper, we have studied about the optimum fabrication condition of the printed Indium Tin Oxide (ITO) layers for the electrical resistance-type sensor application. We have investigated on the substrates surface treatments, mixing ratio of organic binder/ITO powder, and viscosity of the printing paste to determine the optimum condition of the screen printed ITO layer. Also, we found that the printing condition is closely related with the sensor performance. To know the feasibility of printed ITO layer as an electrical resistance-type sensor, we have fabricated the ITO sensors with a printed and sputtered ITO layers. The printed ITO films revealed $10^2$ times higher sensitivity than the sputtered ITO layer. Also, the sputtered ITO layer exhibited an operating temperature of $127^{\circ}C$ at the operating voltage of 5 V. While, in case of the printed ITO layer showed the operating temperature of $27.6^{\circ}C$ in high operating voltage of 30 V. We found that the printed ITO layer is suitable for the various sensor applications.
이중분사기가 장착된 디젤 엔진에서 목질계 열분해유의 적용 가능성에 관한 연구
이석환(Seokhwan Lee),장영운(Youngwoon Jang),김태영(Taeyoung Kim),우세종(Sejong Woo),강건용(Kernyong Kang) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
The vast stores of biomass available in the worldwide have the potential to displace significant amounts of fuels that are currently derived from petroleum sources. Fast pyrolysis of biomass is one of possible paths by which we can convert biomass to higher value products. The wood pyrolysis oil (WPO) have been regarded as an alternative fuel for petroleum fuels to be used in diesel engine. However, the use of WPO in a diesel engine requires modifications due to low energy density, high water contents, low acidity, and high viscosity of the WPO. One possible method by which the shortcomings may be circumvented is to cofire WPO with other petroleum fuels. WPO has poor miscibility with light petroleum fuel oils, the most suitable candidates fuels for direct fuel mixing are methanol or ethanol. Early mixing with methanol or ethanol has the added benefit of significantly improving the storage and handling properties of the pyrolysis oil. For separate injection cofiring, conventional diesel fuels can be fired together with WPO-ethanol blended fuels in a dual-injection diesel engine. In this study, performance and emission characteristics of a dual-injection diesel engine were examined. Results showed that although stable engine operation was possible with dual-fuel combustion, the fuel conversion efficiency was slightly decreased due to high water contents of pyrolysis oil. Regarding to exhaust emissions, NOx and soot emissions were significantly decreased.
배기 열교환기로 인해 증가한 촉매 활성화 시간 감소방안에 관한 연구
이석환(Seokhwan Lee),박정서(Jungseo Park),배충식(Choongsik Bae) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Close-coupled catalyst (CCC) can reduce the engine cold-start emissions by utilizing the energy in the exhaust gas. However, in case the engine is operated at high engine speed and load condition, the catalytic converter may be damaged and eventually deactivated by thermal aging. Excess fuel is sometimes supplied intentionally to lower the exhaust gas temperature avoiding the thermal aging. This sacrifices the fuel economy and exhaust emissions. The heat exchanger was applied in an SI engine to lower the exhaust gas temperature mainly under high load conditions. The heat exchanger was installed between the exhaust manifold and the inlet of the CCC to avoid thermal aging. The exhaust heat exchanger successfully decreased the exhaust gas temperature, which eliminated the requirement of fuel enrichment under high load conditions. The amount of exhaust emissions (HC, CO, NOx) during the cold start increased due to the increment of the catalyst light-off time. This problem could be resolved by adopting the solenoid valve to cut off the coolant at the inlet of the coolant passage of the heat exchanger. New concept of heat exchanger which is combined with the metal catalyst was tested to investigate the possibility of reducing the light-off time.
LPG-DME 혼합연료를 사용하는 전기점화 기관의 연소특성 연구
이석환(Seokhwan Lee),오승묵(Seungmook Oh),최영(Young Choi),강건용(Kernyong Kang),최원학(Wonhak Choi),차경옥(Kyoungok Cha) 한국가스학회 2008 한국가스학회지 Vol.12 No.3
본 연구에서는 DME가 함유된 LPG 연료를 불꽃 점화 기관에서 적용 가능 여부를 실험적으로 살펴보고 있다. LPG와 DME가 함유된 혼합연료로 엔진 구동시 엔진출력, 배출가스 특성, 연소안정성 등의 항목에 대한 실험을 1200~5200 rpm에서 수행하였다. 결과를 살펴보면 20% 내외의 범위에서 DME를 혼합하는 경우 안정된 연소성능을 얻을 수 있었으며 10%까지는 엔진 출력 저하가 거의 없다. 하지만 혼합율이 증가할수록 DME 연료는 LPG보다 에너지 밀도가 낮으므로 출력이 감소하고 제동연료소비율은 증가하는 현상을 보인다. LPG/DME 혼합연료는 향후 DME 시장을 넓혀 나가는 최선의 방법이 될 것이다. In this study, a spark ignition engine operated with the DME blended LPG fuel was investigated experimentally. Performance, emissions characteristics including hydrocarbon, CO, Nox, and combustion stability of an SI engine fuelled with DME blended LPG fuel were examined at 1200~5200 rpm. Results showed that stable engine operation was possible for a wide range of engine loads within 20% mass content of DME fuel. Also, engine output power within 10% mass content of DME fuel was comparable to that of pure LPG fuel operation. However, engine output power was decreased and break specific fuel consumption (BSFC) was severely increased with the amount of blended fuel as the energy content of DME was much lower than that of LPG. DME blended LPG fuel is expected to be potential for enlarging DME market.