• 한국자동차공학회논문집
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• 제14권2호
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• pp.114-120
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• 2006

The basic effects of hydrogen addition for engine performance and emission were investigated in single cylinder research engine. Seven commercial injectors were tested to choose a suitable injector for hydrogen injection prior to its engine implementation. The hydrogen fuel leakage and flow rate were evaluated for each injector and KN3-1(Keihin, CO.) showed the best performance for hydrogen fuel. At the higher excess air ratio(${\lambda}=1.7$, 2.0), the better combustion stability was found with hydrogen addition even though its effect was small at lower excess air ratio (${\lambda}=1.0$, 1.3). Stable operation of the engine was even guaranteed at ${\lambda}=2.0$, if the amount of hydrogen gas was near 15% of total energy. In the lean region, ${\lambda}>1.3$, thermal efficiency was improved slightly while it was not clearly observed at ${\lambda}=1.0$, 1.3. It is considered that, in some cases, high temperature environment due to hydrogen combustion caused further heat loss to surroundings. Except for ${\lambda}=1.0$, with larger amount of hydrogen 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 ${\lambda}=1.0$, 1.3. However, at ${\lambda}>1.3$ its relative amount of emission was low. In addition, the amount of NOx was continuously decreased with hydrogen addition, but, at ${\lambda}=2.0$ the amount of NOx was lowered to 1/100 of that of ${\lambda}=1.0$. THC emission was significantly increased as air/fuel ratio was raised to leaner region due to misfire and partial burn.

• 한국가스학회지
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• 제15권5호
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• pp.50-56
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• 2011

엔진의 제동시의 유효일을 이용하여 고압의 압축 공기를 저장하고 운전 시에는 저장된 압축 공기를 동력원으로 사용하는 신개념의 Air hybrid 엔진의 구현 가능성 검토를 위한 실험적인 연구를 진행하였다. Air hybrid 엔진 시스템의 구현을 위하여 연구용 단기통엔진을 개조하였고, 배기 밸브 중의 하나에 독립 가변 밸브리프트 시스템을 장착하여 압축 행정 동안에 고압의 공기를 저장할 수 있도록 하였다. 또한, 엔진의 구동을 위하여 점화플러그 위치에 공기 분사 모듈을 장착하여 팽창행정 중에 고압의 공기를 분사할 수 있도록 하였다. 압축 공기 저장 모드에서는 800rpm 아이들 조건에서 800 사이클 동안 30리터의 공기 저장 탱크를 최대 13 bar 까지 충전할 수 있었고, 충전된 고압의 공기를 이용하여 800rpm 아이들 조건에서 0.41 bar의 평균도시유효압력의 일을 얻을 수 있었는데 이것은 정상적인 아이들 조건보다 1.1 bar의 유효일이 증가한 것이다.

• 한국수소및신에너지학회논문집
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• 제12권3호
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• pp.169-176
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• 2001

The purpose of study is to obtain low-emission and high-efficiency in LPG engine with hydrogen enrichment. The test engine was named heavy-duty variable compression ratio single cylinder engine (VCSCE). The fuel supply system provides LPG/hydrogen mixtures based on same heating value. Various sensors such as crank shaft position sensor (CPS) and hall sensor supply spark timing data to ignition controller. Displacement of VCSCE is $1858.2cm^3$. VCSCE was runned 1400rpm with compression ratio 8. Spark timing was set MBT without knocking. Relative air-fuel ratio(${\lambda}$) of this work was varied between 0.76 and 1.5. As a result, i) Maximum thermal efficiency occurred at ${\lambda}$ value 1.0. It was shown that thermal efficiency was increased approximately 5% with hydrogen enrichment at same ${\lambda}$ value. ii) Engine-out carbon monoxide (CO) emissions were decreased at a great rate under LPG/hydrogen mixture fuelling. iii) Total hydrocarbon (THC) emission was much exhausted in rich zone, same as CO. But THC was exhausted a little bit more in lean zone. iv) Finally, engine-out oxides of nitrogen (NOx) was increased with ${\lambda}$ value 1.0 zone at a greater rate with hydrogen enrichment due to high adiabatic flame temperature.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.170-177
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• 2006

Hydrogen can extend the lean misfire limit to a large extent when it is mixed with conventional fuels for a spark ignition engine. In this study, hydrogen-enriched gaseous fuels by reforming process were simulated according to their proportions of $H_2$, CO, $CO_2$ and $N_2$ gases. Pure hydrogen and two different hydrogen-enriched gaseous mixtures(A-, B-composition) were tested for their basic effects on the engine performances and emissions in a single cylinder research engine. A- and B-composition showed different results from 100% $H_2$ addition because air/fuel mixtures were more diluted by their additions. Even though the energy fraction of reformed gases was increased, combustion stabilities and lean misfire limits were not sensitively improved. It means that combustion augmentation by $H_2$ addition was offset by the charge dilution of $N_2$ and $CO_2$. In addition, the low flammability of CO gas deteriorated thermal efficiencies. CO emission was drastically increased with B-composition which included higher CO component. However, $NO_x$ was reduced as energy fraction($X_e$) rised except for the case of 100% $H_2$ addition at $\lambda=1.2$ and was, for A-composition, lowered to a factor of ten when compared with that of $H_2$ addition. HC emissions were largely influenced by $COV_{imep}$ due to misfire and partial burns.

• 대한기계학회논문집B
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• 제35권12호
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• pp.1375-1381
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• 2011

커먼레일 분사 시스템이 장착된 대형 단기통 가시화 엔진에서 디젤과 JP-8 의 연소 및 배기 특성을 분석하였다. 두 연료 적용 시, 배기 배출 경향을 분석하기 위해 직접 화염가시화와 이색법을 적용하였다. 연소 과정은 직접 화염 가시화로부터 화염 강도 분석을 통해 이루어 졌다. 이색법 결과는 화염 온도 및 KL 값을 도출하여 분석을 하였다. 직접 화염 가시화 결과, JP-8 연소 시, 점화 지연 기간이 길며, 디젤 연소에 비해 화염이 빠르게 소멸되는 것을 확인하였다. 화염 강도 분석을 통해 디젤 연소의 경우, 연소 전 기간에 걸쳐 높은 화염 강도 수준을 유지하며 화염 지속 기간이 긴 것을 알 수 있었다. 이색법 결과를 통해, JP-8 연소의 경우, 국부적으로 고온의 화염 면이 더 많이 분포하는 것을 확인하였으며, 이는 $NO_x$가 더 많이 배출된 경향을 설명해준다. 또한 KL 치 분석 결과, JP-8 연소 시 낮은 수준의 KL 값이 더 고르게 분포하는 것을 알 수 있었으며, 이는 JP-8 연소 시 스모크 가 덜 배출된 결과를 뒷받침 해준다.