• 한국자동차공학회논문집
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• 제9권4호
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• pp.69-76
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• 2001

VCO nozzle is devised to minimize the HC emission and has been applied on some HSDI diesel engines. But it is not well reported whether VCO nozzle would be advantageous over SAC nozzle in a small HSDI diesel engine. In this paper it is presented that characteristics of VCO and SAC nozzle under common rail fuel injection system and their effects on the performance in a small HSDI diesel engine.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.28-36
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• 2000

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 and its results were compared to standard sac nozzle. The global characteristics of spray, including spray angle, spray tip penetration, and spray pattern were measured from the spray images which were frozen by an instantaneous photography with a spark light source. For better understanding of spray behavior, SMD of the fuel sprays from multi hole nozzles were measured with back light imaging while the sprays from the other holes are covered by a purpose-built nozzle cap. The investigation manifestly reveals the different spray patterns at the beginning of injection produced by VCO nozzles can be identified as three distinct types with their own macroscopic and microscopic characteristics, while macroscopic non-uniformity disappears at 0.9∼1.0ms from the start of injection.

• 한국자동차공학회논문집
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• 제9권2호
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• pp.11-18
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• 2001

To clarify the influence of SAC shape of hole-type diesel nozzle on injection characteristics and spray patterns, the injection rate of three nozzle types(standard SAC nozzle, Needle-cut VCO nozzle and VCO nozzle) were measured by Zeuch's method and pictures of the sprays were taken by CCD camera. As the pump speed became higher, the injection characteristics of the three nozzles were different. Injection rate and perssure curves at the high pressure pipe in Needle-cut VCO nozzle were much more similar to the VCO nozzle than those of the SAC nozzle. When the needle was at pre-lift period for all speeds, the spray of the Needle-cut VCO nozzle showed almost the same shape as the SAC type nozzle. There was no differense in spray pattern at the needle full-lift periods.

• 한국분무공학회지
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• 제9권1호
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• pp.1-7
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• 2004

This paper describes the characteristics of injection rate and macroscopic behavior of fuel spray injected from common-rail type diesel injectors with different nozzle geometries. The injection rates according to the nozzle geometries were measured at different energizing duration of the injector solenoid and injection pressure by using the Bosch's injection rate meter based on the pressure variation in the tube. The spray behaviors injected from the different nozzles were visualized using the spray visualization system composed of an Ar-ion laser, an ICCD camera, and a synchronization system at various injection and ambient pressures. It is revealed that VCO nozzle has higher spray tip velocity at the early stage of injection duration and wider spray cone angle than the mini-sac nozzles. Also the spray cone angle is increased with the increase of nozzle diameter.