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분사시기에 따른 분무유도식 성층연소 DISI 엔진의 분무 및 화염특성
오희창(Heechang Oh),이민석(Minseok Lee),박정서(Jungseo Park),배충식(Choongsik Bae) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, the optical engine experiment was carried out to investigate the effect of injection timing on spray and flame characteristics in a spray guided DISI engine under the lean stratified operation. In the result of the metal engine experiment, at the injection timings where the maximum IMEP were shown, HC and smoke emissions were increased due to effect of under-mixing. Stagnated spray behavior which indicates under-mixing effect was observed at late injection timing by in-cylinder spray visualization. In the result of combustion visualization, various form of flame were shown as injection timing was changed. In the advanced injection timing, stratified combustion showed similar characteristics of lean premixed combustion. However, as the injection timing was retarded, flame showed diffusion-dominant flame characteristic.
직접 화염 가시화를 통한 직접분사식 가솔린 엔진의 성층연소과정 및 입자상 물질 배출 특성에 대한 연구
오희창(Heechang Oh),정진영(Jinyoung Jung),배충식(Choongsik Bae) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
An experimental study was carried out to investigate the combustion process and PM emission characteristics in a spray guided direct injection spark ignition (DISI) engine under lean stratified operation. In-cylinder pressure analysis, exhaust emissions measurement, and visualization of the spray and combustion were applied. Combustion process in a stratified DISI engine was found to be followed 3 major process; the premixed combustion which shows faster combustion speed and high intensity of heat release rate, mixing controlled combustion showing high intensity of luminous flame and lean premixed combustion of which combustion speed is low with smaller intensity of heat release rate. Luminous sooting flame during the combustion process is identified that it represents incylinder formation of PM. PM emission was verified that it is originated from the locally rich area in the stratified mixture which was not burned during the main combustion propagating. Result of incylinder spray visualization and PLIF mixture visualization in a constant volume chamber supported this explanation.
직접분사식 가솔린 엔진에서 에탄올 혼합연료의 분무 및 연소특성
오희창(Heechang Oh),Wang Hua,오창훈(Changhoon Oh),박정서(Jungseo Park),배충식(Coongsik Bae) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
An experimental study was carried out to investigate the effect of ethanol concentration in ethanol blended gasolone on spray characteristics, engine performance and emissions in a single cylinder spray guided direct injection spark ignition engine. The planar laser induced fluorescence and planar Mie scattering macroscopic spray imaging were conducted using simulated fuel. Ethanol showed faster evaporation, enhanced local homogeneity and smaller liquid phase area near the spark plug. The For the engine experiment, it was shown that increased ethanol concentration in ethanol blened gasoline gives wider stratified combustion range in terms of injection timing due to faster evaporation, lower combustion instability and NOx emission due to enhanced local homogeneity and increased IMEP because additional retardation of injection is available.
성층희박연소 운전조건에서 분사압과 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 연소특성
오희창(Heechang Oh),이민석(Minsuk Lee),배충식(Choongsik Bae) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
In this study, single cylinder engine experiment was carried out to investigate combustion characteristics spray guided direct injection spark ignition engine. In the result of engine experiment, it was shown that flammable window of injection timing was existed. The combustion efficiency increased with retarding EOI, reaching a peak value, subsequent to decrease again. These results were likely due to the effect of ambient pressure on stratified-premixed mixture preparation. 150 bar injection pressure condition and retarded injection timing from the best combustion efficiency injection timing showed the highest IMEP value due to the advanced combustion phase of the maximum combustion efficiency condition. HC emission showed same trend of combustion efficiency, and smoke emission was increased as injection timing was retarded due to the increased locally rich area in the high ambient pressure. NOx emission showed decreasing trend as injection timing was retarded. This is likely due to the maximum in-cylinder temperature was decreased with retarded combustion phase.
오희창(Heechang Oh),Wang Hua,박정서(Jungseo Park),배충식(Choongsik Bae) 한국자동차공학회 2009 한국자동차공학회 부문종합 학술대회 Vol.2009 No.4
The direct injection into the cylinders has been regarded as a way of the reduction in fuel consumption and some pollutant emissions in gasoline engine. Its spray is of paramount importance in that the primary atomization process must meet the requirement of quick and complete evaporation and combustion. And the spray geometry must be stable and have robust against pressure change inside of the cylinder. The effect of injection signal, such as induced voltage and nozzle opening/closing time on the spray characteristics including spray geometry and atomization were investigated in a constant volume chamber by using gasoline direct injection piezo actuated outward-opening injector. The macroscopic, microscopic Mie scattering images were taken, Phase doppler anemometer technique was applied to measure droplet size. And injection rate was measured by Bosch method to evaluate the response characteristics of injection.
성층희박연소 운전조건에서 다단분사에 따른 분무유도식 직접분사 가솔린엔진의 연소특성
오희창(Heechang Oh),이민석(Minseok Lee),박정서(Jungseo Park),배충식(Choongsik Bae) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
In this study, the single cylinder engine experiment was carried out to investigate the effect of multiple injections on stratified combustion characteristics in a spray guided direct injection spark ignition engine. In the result of engine experiment with the single injection, indicated mean effective pressure was increased as injection timing was retarded to top dead center due to the increased effective work. However, the retardation of the injection timing was limited by the misfire occurrence resulted from the locally rich mixture generation under the high ambient pressure. Moreover, at the injection timing where the maximum IMEP was shown, HC and smoke emissions were increased due to the locally rich area of the stratified mixture. The multiple injection strategy was applied to enhance the local homogeneity of the stratified mixture. In the result of engine experiment with the double injection, IMEP and combustion efficiency were increased. As an index of combustion instability, COV of IMEP was decreased significantly with the double injection. This result implies that the local homogeneity of the stratified mixture was enhanced by the double injection. HC and CO emissions were decreased significantly with the double injection due to the enhanced local homogeneity of the stratified mixture. NOx emissions were increased due to the increased in-cylinder temperature resulted by more activated combustion. With the triple injection, the flammable injection timing window became narrower. Furthermore, IMEP and combustion efficiency were decreased. This is likely because the stratified mixture was formed on the upper position of the spark plug due to then shortened spray penetration.
성층희박연소 운전조건에서 분사시기에 따른 분무유도식 직접분사 가솔린엔진의 분무 및 화염특성
오희창(Heechang Oh),이민석(Minsuk Lee),박정서(Jungseo Park),배충식(Choongsik Bae) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.3
분무유도식 DISI엔진의 성층연소운전조건에서 분무 및 화염특성에 대한 실험적 연구가 수행되었다. 연소가시화를 통하여 성층연소 DISI의 연소는 희박 예혼합 연소와 확산연소의 성격을 모두 가지고 있는 것으로 확인되었다. 분사시기에 따른 혼합기 형성특성이 연소의 특성을 결정하는 중요한 인자임을 관찰하였다. 분무와 혼합기 가시화를 통해 낮은 분위기압에서의 over-mixing , 높은 분위기압에서의 under-mixing이 발생하는 것을 확인하였으며 이러한 혼합기 형성과정의 결과에 따라 화염특성, 연소효율 등의 연소특성이 결정되는 것을 살펴볼 수 있었다. 또한, NOx, IMEP도 분사시기에 따른 경향성을 보였으며, 분사시기에 따른 연소상의 변화에 의한 영향임을 확인하였다. An experimental study was carried out to investigate the effects of the injection timing on the spray and combustion characteristics in a spray-guided direct-injection spark-ignition (DISI) engine under lean stratified operation. An in-cylinder pressure analysis, exhaust emissions measurement, and visualization of the spray and combustion were employed in this study. The combustion in a stratified DISI engine was found to have both lean premixed and diffusion controlled flame combustion characteristics. The injection timing condition corresponding to the stratified mixture characteristics was verified to be a dominant factor for these flame characteristics. For the early injection timing, a non-luminous blue flame and low combustion efficiency were observed as a result of the lean homogeneous mixture formation. On the other hand, a luminous sooting flame was shown at the late injection timing because of an under-mixed mixture formation. In addition, the smoke emission and incomplete combustion products were increased at the late injection timing as a result of the increased locally rich area. On the other hand, the NOx emissions decreased and IMEP increased as the injection timing retarded. The combustion phasing produced by the injection timing was verified as the reason for this observation.
다운사이징 GDI엔진에서 TiAl 터빈휠 터보차저의 적용에 따른 성능 특성
정진영(Jinyoung Jung),오희창(Heechang Oh),배충식(Choongsik Bae) 한국자동차공학회 2013 한국자동차공학회 부문종합 학술대회 Vol.2013 No.5
In this study, steady and transient tests in a multi-cylinder engine were carried out to investigate performance of turbocharger equipped with TiAl alloy turbine wheel. TiAl alloy has low rotational inertia compared to Inconel 718 alloy, conventional turbine wheel material. In the result of the engine experiment, the boost pressure and turbocharger speed started to increase at 12 bar BMEP. In addition, the turbine wheel faced under pulsating flow condition even in steady engine operation condition. The compressor total-to-total pressure ratio of TiAl turbocharger was higher under wide open throttle condition due to low inertia of TiAl turbine wheel. The efficiency of TiAl turbocharger was also higher than that of Inconel 718 turbocharger. In the transient test, time for boost pressure build-up of TiAl turbocharger was shorter than that of Inconel 718 turbocharger, and turbocharger speed of TiAl turbocharger was also higher. However, even though time for pick engine torque was shorter in case of TiAl turbocharger, the pick engine torque of Inconel 718 turbocharger was higher.