• 한국분무공학회지
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• 제22권1호
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• pp.1-7
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• 2017

Recently, Performance and fuel efficiency of gasoline engines have been improved by adopting direct injection (DI) system instead of port fuel injection (PFI) system. However, injecting gasoline fuel directly into the cylinder significantly reduces the time available for mixing and evaporation. Consequently, particulate matters(PM) emissions increase. Moreover, as the emission regulations are getting more stringent, not only the mass but also the total number of PM should be reduced to satisfy the Euro VI regulations. Increasing the fuel injection pressure is one of the methods to meet this challenge. In this study, the effects of increased fuel injection pressures on combustion and emission characteristics were experimentally examined at several part load conditions in a 1.6 liter commercial gasoline direct injection engine. The main combustion durations decreased about $2{\sim}3^{\circ}$ in crank angle base by increasing the fuel injection pressure due to enhanced air-fuel mixing characteristics. The exhaust emissions and number concentration distributions of PM with particle sizes were also compared. Due to enhanced combustion characteristics, THC emissions decreased, whereas NOx emissions increased. Also, the number concentrations of PM, larger than 10 nm, also significantly decreased.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.182-189
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• 2005

In order to investigate the effect of premixed gasoline, diesel fuel, and n-heptane charges on the combustion and exhaust emission characteristics in a direct injection (DI) diesel engine, the experimental studies are performed. The premixed fuels are injected into the premixing chamber that installed upstream of the intake port in order to minimize the inhomogeneity effect of premixed charge. The injection nozzle for directly injected fuel is equipped in the center of the combustion chamber. The air temperature control system is equipped in the intake manifold to examine the effect of air temperature. The experimental results of this study show premixing fuel is effective method to reduce the NOx and soot emissions of diesel engine. NOx emissions are linearly decreased with increasing premixed ratio for the three kinds of premixed fuels. The heating of intake air $(80^{\circ}C)$ reduced the deterioration of BSFC in high premixed ratio, because it promotes evaporation of premixed diesel droplet in the premixing chamber.

• International Journal of Automotive Technology
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• 제7권5호
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• pp.585-593
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• 2006

The effect of the shape of the side wall on vaporization and fuel mixture were investigated for the impinging spray of a direct injection(DI) gasoline engine under a variety of conditions using the LIEF technique. The characteristics of the impinging spray were investigated under various configurations of piston cavities. To simulate the effect of piston cavity configurations and injection timing in an actual DI gasoline engine, the parameters were horizontal distance from the spray axis to side wall and vertical distance from nozzle tip to impingement plate. Prior to investigating the side wall effect, experiments on free and impinging sprays for flat plates were conducted and these results were compared with those of the side wall impinging spray. For each condition, the impingement plate was located at three different vertical distances(Z=46.7, 58.4, and 70 mm) below the injector tip and the rectangular side wall was installed at three different radial distances(R=15, 20, and 25 mm) from the spray axis. Radial propagation velocity from spray axis along impinging plate became higher with increasing ambient temperature. When the ambient pressure was increased, propagation speed reduced. High ambient pressures tended to prevent the impinging spray from the propagating radially and kept the fuel concentration higher near the spray axis. Regardless of ambient pressure and temperature fully developed vortices were generated near the side wall with nearly identical distributions, however there were discrepancies in the early development process. A relationship between the impingement distance(Z) and the distance from the side wall to the spray axis(R) was demonstrated in this study when R=20 and 25 mm and Z=46.7 and 58.4 mm. Fuel recirculation was achieved by adequate side wall distance. Fuel mixture stratification, an adequate piston cavity with a shorter impingement distance from the injector tip to the piston head should be required in the central direct injection system.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.421-428
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• 2007

This paper investigates the combustion and emission characteristics of a compression ignition engine fueled with neat and blended Shell's gas-to-liquid (GTL) fuel, which was derived from natural gas through the Fischer-Tropsch process. The experiments were conducted in a 6-cylinder DI diesel engine with pump timing settings of $6^{\circ},\;9^{\circ}\;and\;12^{\circ}$crank angle before TDC over ECE R49 and US 13-mode cycles separately and compared to a conventional diesel fuel. The results show that GTL exhibited almost the same power and torque output, improved fuel economy and effective thermal efficiency. It was found that GTL displayed lower peak in-cylinder combustion pressure and maximum heat release rate (HRR), the timings of the peak pressure and the maximum HRR were generally delayed, and the combustion durations were almost equivalent for diesel and GTL under the same speed-load condition. The results also indicate that, compared to diesel fuel, GTL blends showed a trend forward decreasing four regulated emissions simultaneously and a higher GTL fraction in blends contributing to further reductions in the emissions. In particular and on average, neat GTL significantly reduced HC, CO, NOx and PM by 16.4%, 17.8%, 18.3% and 32.4%, respectively, for all cases.

• 동력기계공학회지
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• 제19권2호
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• pp.49-56
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• 2015

As an alternative fuel that can be used in SI engine, LPG is one of clean fuels with larger H/C ratio compared to gasoline, low $CO_2$ emission, and small amount of pollutants such as sulfur compounds. When LPG is used in spark ignition engine, volumetric efficiency of the engine can be improved and pumping loss can be reduced by performing direct injection into the combustion chamber instead of port fuel injection. LPG-DI engine allows for lean combustion and stratified combustion under low load. In case of stratified combustion, air fuel ratio can be greatly increased compared to theoretic mixture ratio combustion. Improved thermal efficiency of the engine and reduced pumping loss can be expected from stratified combustion. Accordingly in this study, an experimental apparatus for visualization was designed and manufactured to study the combustion process of LPG after injection and ignition, intended to examine ignition probability and combustion characteristics of spark ignition direct injection(SIDI) LPG fuel. Ambient pressure, ambient temperature and fuel injection pressure were found as important variables that affect ignition probability and flame propagation characteristics of LPG-air mixture. Also, it was verified that the injected LPG fuel can be directly ignited by spark plug under appropriate ambient conditions.

• 대한기계학회논문집B
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• 제35권2호
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• pp.137-143
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• 2011

본 연구는 4실린더 커먼레일 디젤엔진에 바이오디젤 혼합 디젤연료를 적용하였을 경우 엔진의 연소특성과 배출물 저감효과를 실험적으로 구한 것이다. 실험 연료는 바이오디젤 20%와 디젤연료 80%(체적분율)를 혼합한 BD20과 저유황디젤연료(ULSD)를 사용하였으며, 연료분사압과 엔진회전수를 변수로하여 실험을 수행하였다. 실험결과 B20과 ULSD 모두 연료분사압력이 증가함에 따라 NOx 배출농도는 증가하고, Soot 배출량은 감소하는 경향을 나타내었다. 특히 BD20의 경우 ULSD와 비교하여 NOx 배출농도는 다소 증가하였으나, Soot 배출량은 현저하게 감소하였다. 또한, 회전속도가 1000rpm에서 2000rpm으로 증가함에 따라 NOx 배출농도는 감소하고, Soot 배출량은 낮은 분사압력에서 현저히 증가하는 경향을 나타내었다.

• 해양환경안전학회지
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• 제14권1호
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• pp.83-87
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• 2008

산유국으로부터 에너지 독립을 하고 대기오염방지를 위한 배기배출물을 저감시키기 위하여 대체연료에 많은 관심을 가지고 있다. 폐유나 새로운 식물성 기름과 동물성 기름으로부터 생성할 수 있는 바이오디젤유가 압축점화기관인 디젤기관에 구조적인 변화없이 사용될 수 있다. 이 논문에서는 4행정 직접분사식 디젤기관을 이용하여 순수 디젤유와 바이오디젤 혼합유(바이오디젤 10% 및 20% 함유)의 연료소비율과 배기배출물에 미치는 영향을 제시했으며, 특히 실험에 사용된 바이오디젤 연료는 우리 실험실에서 유채유로부터 직접 생산되었다. 이 연구 결과 바이오디젤 혼합유가 디젤유 보다 연료소비율과 질소산화물은 약간 증가 되었고 일산화탄소와 매연은 상당히 감소되었다.

• 대한기계학회논문집B
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• 제34권12호
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• pp.1043-1050
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• 2010

HCCI엔진에는 농도성층화와 열적성층화가 존재하고, 이것들은 착화와 연소과정에 영향을 미치고 있다. 본 연구에서는 예혼합기의 불균질성이 HCCI연소과정에 미치는 영향에 대해서 조사하였다. 우선 4행정광학엔진을 이용하여 잔류가스가 있는 경우와 급속압축장치를 이용하여 잔류가스가 없는 경우의 예혼합기의 불균질성에 대하여 비교분석하였다. DME를 연료로 이용하고 프래밍카메라를 사용하여 2차원화학발광이미지를 취득하였다. 그 결과, 잔류가스가 있는 불균질 한 경우에 4행정엔진실험에서는 연소현상이 공간적으로 연소현상의 시간차이가 발생하였다. 잔류가스가 없는 급속압축장치의 실험에서는 4행정기관의 결과에 비해서 더 적은 공간적인 변화가 존재하는 것을 알 수 있었다.

• 한국가스학회지
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• 제20권1호
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• pp.52-61
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• 2016

액화석유가스는 환경 친화적이며 에너지 효율성과 출력성능이 뛰어나 실용성이 높고, 경쟁연료에 비해 가격 경쟁력이 우수하기 때문에 촉망받는 대체연료 중 하나로 간주된다. 스파크점화 엔진에서 직분식 기술은 엔진 체적효율을 눈에 띄게 증가시키며, 상대적으로 더 높은 연소효율이 가능한 성층급기를 이용해 엔진을 작동시킨다. 본 연구에서는 가솔린직접분사 엔진의 원리를 적용하여 가시화 시스템을 장착한 연소실을 설계하였다. 이를 통해 스파크점화직분식 LPG의 점화성과 화염전파 과정을 디지털 방식으로 기록하고 분석하였다. 이러한 연구의 결과는 스파크점화직분식 LPG 엔진의 설계 및 최적화를 위한 광범위한 기초 자료로서 기여하고자 한다.

• 에너지공학
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• 제6권2호
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• pp.212-219
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• 1997

본 연구에서는 경유-물 유화연료를 디젤엔진에 적용하였을 때의 엔진의 성능 및 배기배출물 특성에 대해 고찰하였다. 그 결과, 초음파장치(40 KHz, 200W)로 제조한 경유-물 유화연료 운전시, 경유운전시에 비해 연료소비율(함수율 30%시 최대 28% 감소)과 매연(함수율 30%시 최대 60% 감소) 및 CO(할수율 30%시 최대 79% 감소)의 현격한 개선효과를 보았다. 이러한 플러스적인 효과는 유화연료의 미세폭발에 의한 것으로, 초음파에너지로 유화연료를 제조함과 동시에 엔진내로 공급하는 것이 디젤기관의 배기배출물과 연료소비율을 동시에 개선시킬 수 있는 가장 유력한 방법일 것으로 판명되었다. 그러나, 유화연료를 사용한 경우 상대적으로 경유의 유입량 자체가 줄어들게 됨으로써 엔진의 출력 및 토크는 오히려 감소하였다.