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우영민(Youngmin Woo),배충식(Choongsik Bae),오승묵(Seungmook Oh),강건용(Kernyong Kang) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Lean bum was considered to overcome high thermal load and improve fuel economy in heavy duty SI engine. However, lean bum generally causes unstable engine operation due to combustion instability such as cyclic variation, misfire, or partial burning. To overcome such undesirable phenomena charge stratification inside the engine cylinder through fuel injection strategy was utilized and flow field enhancement through intake port and piston shape was adopted.<br/> In this study, tile effects of swirl ratio and piston bowl shape on tile mixture preparation were investigated. High intensity of squish flow as well as swirl flow was acquired by the enlarged piston squish area and helical intake port. To obtain two dimensional fuel distribution planar ~laser induced fluorescence (PLIF) was used. Acetone was excited by KrF excimer laser (248nm) and its fluorescence image was acquired by ICCD camera. Fuel injection strategy with respect to the intake process was found to have the key role of tile whole stratification process. The intense squish flow was found to be effective to place relatively rich mixture to tile vicinity of spark plug in tile end period of compression process.<br/>
연료-공기 공급방식에 따른 수소 프리피스톤 엔진 발전기의 운전 특성
우영민(Youngmin Woo),장진영(Jin Young Jang),이준혁(Jun-hyuk Lee),이용균(Yongnyun Lee),이영재(Youngjae Lee) 한국자동차공학회 2012 한국자동차공학회 지부 학술대회 논문집 Vol.2012 No.10
A power generation system which utilizes a hydrogen fueled free piston engine and a linear generator is under development. Free piston engine gives power output more efficiently compared to the conventional reciprocating piston engines, because it doesn"t have a crank mechanism which brings out additional mechanical loss. In addition, if hydrogen fuel is used in a free piston engine, it is possible to make exhaust emission level almost zero without sacrificing the efficiency. In this study, a two-stroke twin cylinder free piston engine was developed and a linear generation system was incorporated in between the two cylinders to give electricity as well as the start of the engine. It was possible to operate the engine at the frequency above 22 Hz. The free piston engine was found to give different combustion characteristics with the fuel-air supply strategy. Since the exhaust port of the test engine is fixed at 75mm ATDC, the scavenging process is controled by the intake air pressure as well as the intake valve open timing and duration. In addition, hydrogen fuel injection timing was carefully chosen to trap the fuel inside the cylinder with minimizing the amount going out along with the burned gas to the exhaust port. As a result, the power output of the test engine showed two times bigger in the best case than the worst one with the same fuel quantity.
EGR 성충화가 액상 분사 LPG 엔진의 희박연소에 미치는 영향
우영민(Youngmin Woo),배충식(Choongsik Bae),오승묵(Seungmook Oh),강건용(Kernyong Kang) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
Stratified EGR (Exhaust Gas Recirculation) achieves not only reductions in NOx emission and fuel consumption but also combustion stability improvement for highly diluted mixture. In this study, the timing and duration of a fast-response solenoid valve installed in the midst of EGR line was controlled to form the axial stratification of EGR within the cylinder. Lean burn of LPG with both stratified and homogeneous EGR was examined in terms of the rate of heat release, combustion stability (or EGR tolerance), fuel consumption and engineout emissions. Since stratified EGR showed faster combustion and improvement in combustion stability, more EGR amount was admitted and more reduction of NOx emission with less increase in HC emission was attained with stratified EGR than homogeneous EGR.
우영민(Youngmin Woo),염기태(Kitae Yoem),장진영(Jinyoung Jang),배충식(Choongsik Bae) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
Exhaust Gas Recirculation (EGR) system was used to reduce NOx emissions, to improve fuel economy and to suppress knock since it offers the benefits of charge dilution. In this research EGR was adopted to reduce the thermal load on the exhaust manifold, since the reduced gas temperature is desirable for the reliability of an engine in light of both thermal efficiency and material issue of exhaust manifold. However, the occurrence of excessive cyclic variation with high EGR rates brings about an undesirable combustion instability within the engine cylinder resulting in the deterioration of both engine performance and emissions.<br/> For a LPG fueled engine, use of mixer and vaporizer gives its way to liquid phase port injection. Improved volumetric efficiency gives more power and accurate air-fuel ratio gives less amount of hazardous emission. In this research, the investigation of the effects of EGR on the reduction of thermal loading at exhaust manifold was performed in a single cylinder liquid-phase LPG injection engine. The effects of EGR variables (a wide range of EGR rates and EGR Temperature) on power and emission characteristics were also investigated As a result, the optimum EGR rate was derived effectively as a function of the operating conditions.
[가솔린엔진부문] 냉시동시 연료 분사 특성이 HC 배출에 미치는 영향에 대한 실험적 연구
우영민(Youngmin Woo),이용표(Youngpyo Lee),배충식(Choongsik Bae) 한국자동차공학회 1999 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1999 No.11_1
Fuel system directly contributes to the unburned hydrocarbon formation in spark ignition engines. Depending on the injector type the spray characteristics is changed and subsequently affect following combustion. In port fuel injection SI engine most of the hydrocarbon(HC) emission is ascribed to the fuel behavior during cold starting and warm-up period. During this period it is said that intake port and cylinder wall wetting is significantly affect the combustion and HC emission characteristics. Spray behavior with regard to the injectors was characterized qualitatively and spray pattern was evaluated quantitatively with patternator. Using test rig, the wall wetting phenomena was experimentally investigated. HC emission was measured with varying coolant temperature by FR-FID(Fast Response Flame Ionization Detector) at steady idling engine operation.
EGR 성층화가 액상 분사 LPG 엔진의 성능에 미치는 영향
우영민(Youngmin Woo),배충식(Choongsik Bae),오승묵(Seungmook Oh),강건용(Kemyong Kang) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
EGR (exhaust gas recirculation) utilizes the diluents into the engine cylinder to control combustion leading to enhanced fuel economy and reduced emissions. However, with high diluent rate, the occurrence of excessive cyclic variation brings about an undesirable combustion instability resulting in the deterioration of engine performance. Proper stratification of diluent could improve the combustion stability under high diluent environment.<br/> EGR stratification within the cylinder was made by adopting a fast-response solenoid valve in the midst of EGR line and controlling its timing and duty. With supplying EGR in both homogeneous mode and stratified mode, thermodynamic heat release and flame propagation characteristics were investigated in an optically accessible single cylinder engine. Shorter burning duration and faster flame propagation were found in the case of stratified EGR than homogeneous EGR. PLIF images gave the EGR distribution within cylinder to show that EGR occupied the lower part of cylinder through the stratification process and this could help reducing the burning duration.<br/>
하이브리드차량 연비측정 시험방법 표준화를 위한 기술기준 연구
우영민(Youngmin Woo),권오석(Ohseuk Kwon),김강출(Gangchul Kim),이호길(Hokil Lee),서영호(Youngho Seo),김병수(Byoungsoo Kim),이영재(Youngjae Lee) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Since hybrid electric vehicles (HEV) use a secondary battery as well as an internal combustion engine, its fuel economy is significantly affected by the initial state of charge (SOC). Moreover, SOC changes continuously as the battery drives the vehicle and is recharged by engine or regenerative braking. It gives quite different characteristics compared with the conventional vehicles during the chassis dynamometer test. The relationship between the measured fuel economy and battery current balance was investigated for the two hybrid electric vehicles, the Toyota PRIUS and Honda CIVIC. As a result, a new HEV specific procedure is proposed to give fuel economy value which accounts for the battery current balance.