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Oh, Seungmook,Kim, Changup,Lee, Yonggyu,Yoon, Sungjun,Lee, Junsoon,Kim, Junghwan Elsevier 2019 Energy Conversion and Management Vol.201 No.-
<P><B>Abstract</B></P> <P>Hydrogen is gaining substantial attention from both public and industries for its promising characteristics as an alternative fuel for internal combustion engines. High flame speed, strong knock resistance, as well as zero carbon dioxide emission put hydrogen ahead of most other alternative fuels. The fast flame and low knock tendency are favorable traits for high compression ratio, which is a key enabler for high efficiency. In this study, engine experiments were conducted to investigate the combustion and emission characteristics of a high-compression ratio, single-cylinder, spark-ignition engine with hydrogen-rich gas mixture. The compression ratio was varied from 10:1 to 17:1 by modifying the piston bowl geometry. The engine load was adjusted through the air fuel ratio by changing the mass flow rate of the fuel gas while the intake throttle valve maintained at wide open position. The consequent excess air to fuel ratio was varied from 3.5 at the lightest to 1.0 at the highest load operation. Spark timing sweep was performed to determine the optimal timings at various load conditions. The highest compression ratio in the present study, 17.0, yielded the highest indicated thermal efficiency, which was 51% at medium load condition. High and low load operations exhibited lower thermal efficiencies, with the estimated excess air to fuel ratio approaching 1.0 and 3.5, respectively. The optimal spark timings of the high load conditions under high compression ratios were retarded to top-dead center or later to avoid backfire and pre-ignition. Results of efficiency loss analysis show that high-temperature combustion is the major contributor to efficiency reduction at high load conditions, whereas the gas exchange process and elongated burn duration were the largest contributors at low load conditions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of compression ratio on hydrogen-rich gas mixture was investigated. </LI> <LI> Highest efficiency at a compression ratio of 17:1 was 51% at medium load condition. </LI> <LI> High-temperature combustion is a major source of efficiency reduction at high load. </LI> </UL> </P>
엔진연소실에서 아세톤 형광을 이용한 공연비 측정기법 연구
오승묵(Seungmook Oh),강건용(Kernyong Kang),박승재(Seungjae Park),허환일(HwanilHuh) 한국자동차공학회 2002 한국자동차공학회 Symposium Vol.2002 No.11
Planar laser induced fluorescence(PLIF) has been widely used to obtain two dimensional fuel distribution.<br/> Preliminary investigation was performed tomeasure quantitative air excess ratio distribution in an engine fueled with<br/> LPG. It is known that fluorescence signal from acetone as a fluorescent tracer is less sensitive to oxygen quenching<br/> than other dopants. Acetone was excited by KrF excimer laser (248nm) and its fluorescence image was acquired by<br/> ICCD camera with a cut-off filter to suppress Mie scattering from the laser light. For the purpose of quantifying PLIF<br/> signal, an image processing method including the correction of laser sheet beam profile was suggested. Raw images<br/> were divided by each intensity of laser energy and profile of laser sheet beam. Inhomogeneous fluorescence images<br/> scaled with the reference data, which was taken by a calibration process, were converted to air excess ratio<br/> distribution. This investigation showed instantaneous quantitative measurement of planar air excess ratio distribution<br/> for gaseous fuel.
과급에 의한 바이오디젤의 저온연소 운전영역 확장에 관한 연구
오승묵(Seungmook Oh),장재훈(Jaehoon Jang),이용규(Yonggyu Lee),이선엽(Sunyoup Lee) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
바이오디젤 연료는 그 안에 포함된 산소성분으로 인해 압축착화엔진에 사용했을 때 일반디젤 연료보다 더 적은 입자상 물질을 배출한다. 따라서 이 연료를 저온연소 기법에 적용하는 경우 보다 효과적으로 NOx-PM을 동시 저감할 수 있고 그로부터 저온연소 운전영역의 확장을 기대할 수 있다. 이번 연구에서는 일반디젤과 대두유 기반의 바이오디젤 연료를 이용하여 Dilution controlled regime에서의 저온연소 운전을 구현하고 성능 및 배기 특성을 조사하였다. 엔진 실험 결과로부터 바이오디젤 연료의 경우 디젤에 비해 약 14% 낮은 발열량에도 불구하고 높은 세탄가 및 함산소 성질로 인한 연소효율 증가로 동일 연료량 분사 시 이보다 더 낮은 약 10~12% 정도의 출력이 감소함을 볼 수 있었다. 배기 측면에서도 바이오디젤 내 산소원자가 입자상물질의 산화반응을 촉진하여 최대 90%의 smoke 저감이 가능하며 THC, CO 역시 감소함을 관찰하였다. 또한 엔진 과급 실험으로부터 과급을 사용하여 저온연소 및 바이오디젤 사용으로 인한 출력 저하를 개선할 수 있음을 확인하였으며 과급과 바이오디젤 연료의 동시적용을 통해 더 적은 EGR 가스 투입으로도 저온연소에 상응하는 PM-NOx 동시 저감이 가능함을 보여주었다. 이런결과는 결국 이와 같은 과급 및 바이오디젤 연료의 적절한 조합으로부터 엔진 출력 향상과 배기특성 개선이 동시에 달성할 수 있음을 의미하며 이로부터 운전영역의 확대가 가능함을 제시하였다. Due to its O content, biodiesel (BD) has benefits in lowering PM in CI engines. This ability can make the fuel considered as one of the best candidates for LTC operation since use of BD can extend the regime for simultaneous reduction of PM and NOx. Thus, in this study, LTC operation was realized with BD and diesel at 5~7% O2 fraction. Engine test results show that use of BD raised efficiency and reduced emissions such as PM, THC and CO while IMEP was decreased by 10~12% due to lower LHV of the fuel. Especially, smoke was suppressed by up to 90% since O atom in BD enhanced soot oxidation reaction. To compensate IMEP loss, turbocharging (TC) was then tested and the results show that not only was power output increased but also PM was reduced further. Moreover, TC in BD engine operation allowed a similar level of reduction in both NOx and PM at 11~12% O2 fraction, meaning that there is a potential to widen the operating range by the combination of TC and BD.
석유액화가스엔진에서 수소첨가에 의한 희박연소 특성 연구
오승묵(Seungmook Oh),김정환(Junghwan Kim),이용규(Yonggyu Lee) 한국추진공학회 2014 한국추진공학회 학술대회논문집 Vol.2014 No.12
Combustion and emission characteristics were investigated in LPG engine with hydrogen addition. At λ=1.7 and 2.0, high combustion stability was found with hydrogen even though its change was small at λ=1.0 and 1.3. Stable operation of the engine was presented even at λ=2.0, if the amount of hydrogen gas was near 63% volume fraction (15% of total energy). High in-cylinder temperature due to hydrogen combustion resulted in further heat loss to surroundings. Except for λ=1.0, with larger blending of hydrogen, CO was reduced significantly but it was not the case at the leaner region. Nitric oxides(NOx) was increased slightly with hydrogen at λ=1.0 and 1.3. However, when λ>1.3, its relative amount of emission was low. NOx was continuously decreased with hydrogen. However, at λ=2.0 NOx was lowered to a factor of 100 at λ=1.0. THC emission was significantly increased as air/fuel ratio close to leaner region due to misfire and partial burn.
직접분사식 LPG 및 가솔린 엔진의 연소 및 배기특성 비교 연구
오승묵(Seungmook Oh),이석환(Seokhwan Lee),조준호(Junho Cho),차경옥(Kyoungok Cha) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
Combustion and emission characteristics of LPG(Liquefied Petroleum Gas) and gasoline fuels were compared in a single cylinder engine with direct fuel injection. While fuel injection pressure and IMEP(indicated mean effective pressure) were varied with 60, 90, 120 bar and 2 to 10 bar, another parameters for the engine operation as engine speed, air excess, and fuel injection timing were fixed at 1500 rpm, 1.0, and BTDC 300 CA respectively. Experimental results show that MBT timing for LPG is less sensitive to IMEP, and its combustion stablility(COVIMEP) is also better than gasoline fuel. However, LPG is found that thermal efficiency has lower values a little due to increase of pumping loss by higher throttling inherently. Gasoline shows longer burn durations in the early stage of combustion(10% MBF), but when considering total burn duration(90% MBF) gasoline was shorter than LPG for over IMEP 7 bar. Hydrocarbon emissions of gasoline rise to a level of three-fold than those of LPG. In addition, nitric oxides has higher values for gasoline but carbon monoxide for both fuels shows similar level for all test conditions
오승묵(Seungmook Oh),김창업(Changup Kim),강건용(Kernyong Kang) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.5_1
The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. At the higher excess air ratio(λ=1.7, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio(λ=1.0, 1.3). Stable operation of the engine was even guaranteed at λ=2.0, if the amount of hydrogen gas was near 15% of total energy. In the lean region, λ>1.3, thermal efficiency was improved slightly while it was not clearly observed at λ=1.0, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for λ=1.0, with larger amount of hydrogen gas addition, CO was reduced drastically but it was emitted more at the leaner region. Nitric oxides(NOx) was increased a little more with hydrogen addition at λ=1.0, 1.3. However, at λ>1.3 its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at λ=2.0 the amount of NOx was lowered to 1/300 of that of λ=1.0. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.