• 한국분무공학회지
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• 제27권2호
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• pp.84-93
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• 2022

To implement carbon-neutrality in transportation sectors until 2050, hydrogen is considered a promising fuel for internal combustion engines because hydrogen does not contain carbon itself. Although hydrogen does not emit CO₂ emission from its combustion process, the low energy density in a volume unit hinders the adoption of hydrogen. Therefore, the understanding of hydrogen jet behavior and measurement of equivalence ratio must be conducted to completely implement the high-pressure hydrogen direct injection. The main objective of this research is feasibility test of hydrogen local equivalence ratio measurement by laser-induced breakdown spectroscopy (LIBs). To visualize the macroscopic structure of hydrogen jet, high-speed schlieren imaging was conducted. Moreover, LIBs has been adopted to validate the feasibility of hydrogen local equivalence ratio measurement. The hydrogen injection pressure was varied from 4 MPa to 8 MPa and injected in a constant volume chamber where the ambient pressure was 0.5 MPa. The increased injection pressure extends the vertical penetration of hydrogen jet. Due to the higher momentum supply when the injection pressure is high, the hydrogen has easily diffused in all directions. As the laser trigger timing has delayed, the low hydrogen atomic emission was detected due to the longer mixture formation time. Based on equivalence ratio measurement results, LIBs could be applied as a methodology for hydrogen local equivalence ratio measurement.

• 한국가스학회지
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• 제26권3호
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• pp.45-53
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• 2022

디젤엔진의 배출물 개선을 위해 탄소수가 낮은 천연가스를 혼합하여 사용하는 천연가스-디젤 혼소 연소가 각광받고 있다. 특히 자발화 특성에 차이가 있는 디젤과 천연가스의 특성을 이용한 반응성 제어 압축착화(reactivity controlled compression ignition, RCCI) 연소 전략을 통해 기존 디젤엔진의 효율과 배출가스를 동시에 개선시키는 연구가 활발하게 진행되어 왔다. 상사점보다 앞당겨진 디젤 직접 분사시기 적용을 통해 실린더 전체 영역의 균일 혼합기를 형성하여 전체적으로 희박한 자발화 기반 연소를 달성함으로써 질소산화물 (NOx) 및 입자상물질 (PM) 저감과 제동열효율 개선을 동시에 달성할 수 있다. 하지만 매우 희박한 저부하 영역에서 불완전 연소량이 증가하는 단점이 존재하며, 안정적인 연소 구현을 위해 디젤 분사시기가 민감하게 제어되어야 하는 어려움도 존재한다. 본 연구에서는 앞서 언급된 저부하 영역에서의 천연가스-디젤 혼소 엔진의 효율 및 배기 개선을 확인하고, 동시에 발전용 엔진 구동 영역에서 디젤 분사시기에 따른 연소안정성을 평가하였다. 실험에는 6 L급 상용디젤 엔진이 사용되었으며, 1,800 rpm, 50% 부하 영역 (~50 kW)에서 실험이 진행되었다. 제동효율 및 연소안정성을 개선하기 위한 전략으로 분무 패턴이 다른 2개의 인젝터를 적용하였으며, 천연가스/디젤 비율과 디젤 분사시기를 바꿔가면서 실험이 진행되었다. 실험 결과, 협각 분사가 추가된 수정 인젝터에서 제동 열효율이 증가하는 것을 확인하였다. 또한 연소안정성 및 출력, 그리고 강화된 배기 규제를 고려하였을 때 수정 인젝터의 분무 패턴이 예혼합연소 형성에 적합하였고 이를 통해 질소산화물 배출량을 Tier-V 기준치인 0.4 g/kWh 이하로 저감함으로써 RCCI 연소 가능 영역을 확장할 수 있음을 실험적으로 확인하였다.

• 한국가스학회지
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• 제20권4호
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• pp.58-64
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• 2016

차량에 사용되는 주엔진은 부하영역 전체에서 효율을 증가시키기 위해 커먼레일 디젤엔진을 사용하고 있다. 그러나, 발전기용 엔진은 아직도 기계적 구성엔진으로 캠으로 구동되는 연료분사밸브가 사용되어지고 있다. 또한, 발전기용 엔진 대부분은 50%이하의 부분부하가 적용되고 있다. 따라서, 전부하에 세팅된 차량용 디젤엔진을 부분부하에서 효율적인 운전을 하기 위해서는 연료분사시기 재조정이 필요하다. 본 연구에서는 시설물에 사용되는 엔진발전기의 운용특성을 파악하여 연료분사시기를 재조정함으로서 부분부하 연료소비율을 개선시킨 결과를 연구하고자 한다.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.135-144
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• 2005

The Effects of intake swirl and combustion parameters on the performance and emission characteristics in a V8 type turbocharged intercooler D.I. diesel engine of the displacement $16.7\iota$ were studied experimentally in this paper. Generally the swirl in the combustion process of diesel engine promotes mixing of the injection fuel and the intake air. Also, TCI diesel engine is put to practically use intercooler in order to increase boost efficiency which is cooled boost air. As a result of steady flow test, when the swirl ratio is increased, the mean flow coefficient is decreased, whereas the Gulf factor is increased. And through engine test, its can be effected to meet performance and emission by optimizing the main parameters; the swirl ratio is 2.25, compression ratio is 17.5, combustion bowl is re-entrant $8.5^{\circ}$, nozzle hole diameter is $\phi0.33^{\ast}3+\phi0.35^{\ast}2$, injection timing is BTDC $12^{\circ}CA$ and turbocharger is T02 model which are compressor 0.6A/R+46trim and turbine 1.0A/R+57trim.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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• pp.37-47
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• 2002

Recently gasoline direct injection method has been applied to gasoline engine to reduce fuel consumption rate by controlling fuel air mixture on lean condition by means of stratified charging, and to reduce simultaneously. Pollutant emissions especially NOx and CO by lowering the combustion temperature. But difficulty of controling local fuel air ratio at ignition area in flammability limit unavoidably appeared, because it is merely controlled by injection timing with spatial and temporal distribution of fuel mixture. In this study, the authors devised a uniquely shaped combustion chamber so called three-chamber GDI engine, intended to keep the more reliable fuel air ratio at ignition area. The combustion chamber is divided into three regions. The first region is in the rich combustion division, where the fuel is injected from the fuel injection valve and ignited by the spark plug. The second region is in the lean combustion division, where the combustion gas from the rich combustion division flows out and burns on lean condition. And the last region is in the main combustion division ie in the cylinder, where the gas from the above two combustion divisions mixed together and completes the combustion during expansion stroke. They found that the stable range of operation of three-chamber GDI engine on low-load condition exists in the lean area of average equivalence ratio. And they also found that the reformed engine reveals less specific fuel consumption and less pollutant emissions compared with conventional carburettor type gasoline engine.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.47-56
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• 2001

Nitrogen oxides(NOx) and smoke emissions of diesel engine are regarded as a source of air pollution, and there is a global trend to enforce more stringent regulations on these exhaust gas emissions. However, the trade-off relation of NOx and smoke is a main obstacle to reduce both of them simultaneously. In this paper, experiments were conducted with an oxygenated fuel(diethyl ether) as an effective way to improve the trade-off relation of NOx and smoke. Exhaust emissions of diesel fuels with DEE were influenced by the additive content of DEE and the injection timing. Especially, DEE effected more at the high engine speed and load than at the low engine speed and load. Diesel fuel blended with DEE 10% was a desirable blend for the simultaneous reduction of NOx and smoke.

• 한국자동차공학회논문집
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• 제11권2호
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• pp.22-30
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• 2003

Engine-out HC emissions were investigated during cold and hot start. The tests were conducted according to engine cooling temperatures which were controlled by simulated coolant temperatures of cold and hot start, on a 1.5L, 4-cylinder, 16 valve, multipoint-port-fuel-injection gasoline engine. Real time engine-out HC emissions were measured at a exhaust port and cylinder head using Fast Response Flame Ionization Detector(FRFID). Unburned hydrocarbons emitted at the cold coolant temperature were much higher than those of the hot coolant temperatures. And the main source of the high HC emission was confirmed as misfire at cold coolant temperature. In addition, the effect of intake valve timing on engine-out HC emissions was investigated. The results obtained indicate that optimized intake phasing provides the potential for start-up engine-out HC emissions reduction.

• 에너지공학
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• 제26권3호
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• pp.71-77
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• 2017

피동고압충수용 혼합형 안전주입탱크 (Hybrid SIT)의 압력평형시간은 냉각수 주입시기를 결정하는 주요인자이다. 한국원자력연구원 (KAERI)에서는 Hybrid SIT에서의 내부 열수력적 거동을 고찰하기 위해 개별효과시험 장치를 구축하였으며, 다양한 운전조건에서의 압력평형시간에 대한 민감도 시험을 수행하였다. 개별효과시험을 통해 압력평형시간을 결정하는 주요인자들을 도출하였으며, 그 중 증기의 벽면응축 및 냉각재와의 직접접촉응축이 압력평형시간을 결정하는 주요 현상임을 파악하였다. 본 연구에서는 개별효과 시험결과들을 이용하여 각각의 응축현상들이 압력평형에 미치는 영향을 정량적으로 분석하고 혼합형 SIT의 압력평형시간을 예측하기 위한 방법론을 제시하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.899-905
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• 2000

The characteristics of air flow and engine performance with swirl ratio variance of intake port In a turbocharged DI diesel engine was studied in this paper. The intake port flow is important factor which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. The swirl ratio for ports was modified by hand-working and measured by impulse swirl meter. For the effects on performance and emission, the brake torque and brake specific fuel consumption were measured by engine dynamometer and NOx, smoke were measured by gas analyzer and smoke meter. As a result of steady flow test, when the valve eccentricity ratio are closed to cylinder wall, the flow coefficient and swirl intensity are increased. And as the swirl ratio is increased, the mean flow coefficient is decreasing, whereas the gulf factor is increasing. Also, through engine test its can be expected to meet performance and emission by optimizing the main parameters; the swirl ratio of intake port, injection timing and compression ratio.

• 한국자동차공학회논문집
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• 제14권1호
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• pp.138-143
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• 2006

Modification of injector, oil ring tension reduction and oil pump rotor re-matching with optimization of relevant engine control parameters could drive fuel consumption reduction of HSDI diesel engine. A 5 holes injector was replaced with a 6 holes with smaller nozzle hole diameter and 1.5 k factor, and evaluated in a view of fuel economy and emission trade-offs. With introducing smaller nozzle hole diameter injector, PM(Particulate Matter) was drastically decreased for low engine load and low engine rpm. Modification of oil pump and oil ring was to reduce mechanical friction and be proved to better fuel economy. Optimization of engine operating conditions was a great help for the low fuel consumption. Influence of the engine operating parameters· including pilot quantity, pilot interval, air mass and main injection timing on fuel economy, smoke and NOx has been evaluated with 14 points extracted from NEDC(New European Driving Cycle) cycle. The fuel consumption was proved to $7\%$ improvement on an engine bench and $3.7\%$ with a vehicle.