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강진석(Jinsuk Kang),배충식(Choongsik Bae) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The break-up zone of diesel spray from a valve covered orifice (VCO) nozzle was visualized to observe the effect of injection rate on spray structure and to obtain the physical insight on the development process of transient diesel spray. The surface shape and internal structure of the diesel spray from a common-rail injection system was visualised with high spatial and temporal resolution under atmospheric ambient condition at room temperature. Highly magnified spray images were presented with common-rail pressure of 39.5MPa and 112MPa from the nozzle exit to about 260 nozzle diameters downstream during injection period A short transition period was found where ligaments were formed on the disturbed liquid column surface, before atomization break-up regime appeared as injection velocity increased. In atomization regime, spray was surrounded by the short and fine ligaments, which were arranged and bent to the direction of spray penetration The internal structure of break-up zone consisted of complicatedly entangled ligaments and dispersed liquid drops. Break-up process occurred simultaneously at spray surface and core rather than gradually propagated from the spray surface. Entrained ambient air penetrating through the crevices of densely packed ligaments seemed to stretch the coherent structure and carry small droplets from the spray surface. The collapse of cavitation bubble might be a cause of ligaments forming near the nozzle exit at the spray core, but the detailed process remains to be identified. Averaged liquid drop size, which was measured at spray downstream with image processing technique, was found to decrease while injection rate increased and higher<br/> common-rail pressure led smaller droplets as expected.<br/>
[디젤엔진부문] VCO 노즐에서 고압으로 분사되는 디젤분무의 특성
강진석(Jinsuk Kang),배충식(Choongsik Bae) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Spray characteristics of diesel fuel injection is one of the most important factors in diesel combustion and pollutant emissions especially in HSDI (High Speed Direct Injection) diesel engines where the interval between the onset of combustion and the evaporation of atomized fuel is relatively short. An investigation into various spray characteristics from different holes of VCO(Valve Covered Orifice) nozzles was performed.<br/> The investigation manifestly reveals the different spray patterns at the beginning of injection produced by YCO nozzles equipped with 2-spring injector can be identified as three distinct types with their own macroscopic and microscopic characteristics, while macroscopic non-uniformity disappears at O.9-1.0ms from the start of injection<br/>
이경민(Kyungmin Lee),강진석(Jinsuk Kang),조원진(Wonjin Jo),표순찬(Soonchan Pyo) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
ECU control parameters were optimized on engine test bench to improve the fuel economy of passenger diesel vehicle. Optimization was performed with model based optimization technique of MATLAB<SUP>®</SUP>. The vehicle NEDC test result with newly optimized ECU dataset showed that the reduction amount of fuel consumption, NOx, and PM were 3.4%, 15%, and 23% respectively. NEDC cycle optimization strategy was setup according to engine load conditions.
커먼레일시스템의 비증발 디젤 분무에서 분사율과 주변기체의 압력에 따른 주변기체 유입
공장식(Jangsik Kong),강진석(Jinsuk Kang),배충식(Choongsik Bae) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Entrainment of ambient gas is a crucial characteristics of transient diesel spray. Recently, it was found that the mass flow rate of ambient gas into transient diesel spray increased with the distance from the nozzle, i.e., axial momentum flow rate of entrained gas increased along spray axis. This tendency is different from the turbulent jet whose momentum flow rate is independent from axial positions.<br/> To understand more detailed spray behaviors, it is necessary to quantify the entrainment characteristics of transient diesel sprays under realistic injection and ambient conditions In this study, measured was the entrained velocity of ambient gas into a diesel spray with LDV (Laser Doppler Velocimetry) technlmique. Non-evaporating transient diesel sprays from a common-rail injection system with triangular injection rate profile were observed. The effects of ambient gas density and nozzle hole geometry were assessed with entrainment coefficient.<br/> There appeared a region where entrainment coefficients were remaining almost constant after onset of entrainment while iIjection rates were changing The effect of common-rail pressure, which altered the slope of injection rate curve, was hardly noticed at this region. Entrainment coefficient increased with ambient gas density, that is, the effect of ambient gas density on entrainment of transient diesel spray is larger than that of turbulent jet whose entrainment coefficient remains constant.<br/> Non-dimensional distance was defined to reflect the effect of nozzle hole diameter and ambient gas density together. Mean value of entrnainment coefficient was found to increase with non-dimensional distance from the nozzle.<br/>