• 한국분무공학회지
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• 제21권1호
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• pp.20-28
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• 2016

This paper presents an experimental study on the GDI injector with Bosch method. The injection characteristics, such as the injection quantity, the injection rate, the maximum velocity of the nozzle exit and the injection delay were studied through the change of the injection pressure, the tube pressure and energizing duration in injection rate measurement device using nheptane. The injection quantity is increased by increasing injection pressure, decreasing tube pressure or increasing energizing duration. As the difference of the injection quantity changed, the shape of injection rate was moved with a constant form. The maximum velocity of the nozzle exit showed a tendency to increase as the injection pressure is increased. However, tube pressure did not affect. Overall, it was confirmed that the closing delay is longer than the opening delay in all conditions. As the injection pressure increased, the result has a tendency to decrease the closing delay, it did not affect the opening delay. Reduction of the closing delay showed the reduction of the injection duration. the tube pressure and energizing duration did not affect the injection delay (opening delay, closing delay).

• 한국자동차공학회논문집
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• 제15권5호
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• pp.24-29
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• 2007

This study aims to provide a fundamental data for directly injected hydrogen fuel engines. Spray, ignition and combustion characteristics of hydrogen were studied using constant volume chamber. For spray visualization, hydrogen was vertically injected into a combustion chamber at various condition, for example, injection pressure, ambient pressure. And an argon laser was used for the shadowgraph photography by applying optical method. Also, to investigate heat-release rate and flame propagations, spark was ignited on hydrogen injected at the different time after injection and the duration of injection was also changed. Processes of ignition and combustion were analyzed by heat-release rate calculated by pressure history and were observed by shadowgraph photography The results gave much knowledge of spray, ignition and combustion characteristics of hydrogen.

• 한국자동차공학회논문집
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• 제2권5호
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• pp.30-40
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• 1994

The direct-injection stratified-charge engine has the advantages of higher thermal efficiency and less CO and $NO_x$ emission levels than conventional spark ignition engines. However, its actual utilization is prevented by high unburned hydrocarbon emission levels during light-load operations. In this paper, fundamental studies were carried out using a pancake type constant volume bomb. The effects of intensification of local premixing by tangential and radial fuel injection were examined experimentally. Unburned hydrocarbon emission levels with radial fuel injection were shown to be lower than those of tangential fuel injection cases. The stratification and mixing process of fuel jet and combustion process were observed by schlieren photography.

• 한국분무공학회지
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• 제15권1호
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• pp.25-30
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• 2010

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail direct injection system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors with different electric driving characteristics, including solenoid-driven and piezo-driven type. Namely three common-rail injectors with different electric current wave were investigated in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. As this research results, it was found that pilot injection of common-rail system was effected by rate of injection with different electrical characteristic for driving the injector.

• 한국자동차공학회논문집
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• 제20권1호
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• pp.68-76
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• 2012

Recently, the important issues of gasoline engine are to reduce the fuel consumption and emission. Thus, many researchers are studying the technology to solve these problems. One approach of these issues is to achieve homogeneous charge combustion and stratified change combustion with various injection strategy. In this study, the combustion characteristics of DISI engine accrding to injection strategy were examined. The effect of injection timing on lean limit A/F were investigated using dual DISI single cylinder. The results show that the engine operation region of dual DISI type engine is larger than that of PFI and DISI type engine cases. Especially, late injection is very effective to extend the operation region more than any other injection timings. In addition, the results show that when the DISI injection ratio is increase, leam limit A/F is improved. It means that the dual injection system car meet with emission regulations and reduce the fuel consumption. Also, combustion pressure of dual injection system is much higher than PFI and DISI injection.

• 동력기계공학회지
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• 제16권3호
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• pp.16-21
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• 2012

Biodiesel is technically competitive with or offers technical advantages over conventional petroleum diesel fuel. Biodiesel is an environmentally friendly alternative liquid fuel that can be used in any diesel engine without modification. In this study, to investigate the effect of fuel injection timing on the characteristics of performance with DBF in DI diesel engine. The engine was operated at five different fuel injection timings from BTDC $6^{\circ}$ to $14^{\circ}$ at $2^{\circ}$ intervals and four loads at engine speed of 1800rpm. As a result of experiments in a test engine, maximum cylinder pressure is increased with leading fuel injection timing. Specific fuel oil consumption is indicated the least value at BTDC $14^{\circ}$ of fuel injection timing.

• 대한기계학회논문집B
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• 제33권9호
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• pp.722-727
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• 2009

The effect of the intake flow on the spray structure of a high pressure 11-hole fuel injector were examined in a single cylinder optical direct injection spark ignition (DISI) engine. The effects of injection timing and in-cylinder charge motion were investigated using the 2-dimensional Mie scattering technique. It was confirmed that in the homogeneous charge mode, the in-cylinder swirl charge motion played a major role in the fuel spray distribution during the induction stroke rather than the tumble flow. But, in the stratified charge mode, the effect of the in-cylinder charge was not so large that the injected spray pattern was nearly maintained and the increase of in-cylinder pressure by the upward moving piston reduced the fuel spray penetration.

• 한국분무공학회지
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• 제6권2호
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• pp.9-15
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• 2001

The internal flow characteristics of a gasoline direct injector have been studied to improve fuel economy and reduce exhaust emissions. Computational Fluid Dynamics (CFD) is used to examine the internal flow of the GDI with the purpose of designing the optimum geometry of the injector. This study tests orifice length, cone angle, swirl angle, orifice diameter and needle lift. The results show that optimum sizes of the orifice length, cone angle, swirl angle, orifice diameter and needle lift are 0.8mm, $140^{\circ},\;120^{\circ},\;80mm\;and\;70{\mu}m$, respectively. The size of the lift does not affect the formation of the air core signficantly near the tip of the needle compared to the ball-type needle. The vena contracta phenomenon near the orifice inlet can be released by smoothing the edge.

• 한국분무공학회지
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• 제23권1호
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• pp.22-29
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• 2018

The purpose of this study is to investigate the macroscopic spray characteristics and spray pattern of a gasoline direct injection (GDI) injector according to the increase of injection pressure. The macroscopic spray characteristics, such as a spray tip penetration and spray angle, were measured and analyzed from the frozen spray images, which are obtained from the spray visualization system including the high-speed camera, light-source, long-distance microscope (LDM). The spray pattern was analyzed through the deviation of the center of the spray plum and images were acquired using Nd: YAG Laser and ICCD(Intensified charge coupled device) camera. From the experiment and analysis, it revealed that the injection pressure have a significant influence on the spray tip penetration and spray pattern. However, the injection pressure have little influence on the spray angle. The increase of injection pressure induced the reduction of a closing delay. In addition, the deviation of spray center increase with the increase of injection pressure and the distance from a nozzle tip.

• 동력기계공학회지
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• 제6권1호
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• pp.5-11
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• 2002