• Journal of ILASS-Korea
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• v.23 no.2
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• pp.96-101
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• 2018

The purpose of this study is to investigate the effect of water injection on combustion characteristics of gasoline direct injection (GDI) engine with turbo-charger under low-load operating condition. The test engine used in this study has four-cylinder and 10.2 of compression ratio. In order to study the effect of water injection ratio on combustion characteristics, the water was injected into the intake port from 10% to 50%, based on fuel injection quantity. From the experiment, it revealed that the water injection induced the improvement of fuel economy because of the advance of spark-timing by the reduction of in-cylinder temperature. In addition, the water injection caused the prolong of extension of the ignition delay and slight increase of burn duration.

• Journal of ILASS-Korea
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• v.26 no.4
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• pp.197-203
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• 2021

In gasoline direct injection injectors, cavitation can be generated inside the hole because of their high injection pressure. In this paper, the effects of cavitation development in injector were investigated depending on the various hole drilling angles were investigated by a numerical method. In order to verify the internal flow model, injection rate and injection quantity of individual holes were measured. The BOSCH long tube method was used to measure the injection rate. As a result, even if the hole diameters were the same, the discharge coefficient differed by up to 10% depending on the hole angle. Moreover, if the hole drilling angle became greater than 30°, the area coefficient and the discharge coefficient decreased as the nozzle outlet was blocked due to cavitation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.335-342
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• 2012

Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.

• Journal of ILASS-Korea
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• v.4 no.4
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• pp.1-8
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• 1999

The concentration and spatial distribution of vapor phases in DI (Direct Injection) gasoline spray were measured quantitatively by exciplex fluorescence method. Fluorobenzene and DEMA (diethylmethylamine) in a solution of hexane were used as the exciplex-forming dopants. The fluorescence intensity of vapor phase were obtained by ICCD camera with the appropriate filter The relationship between fluorescence intensity and vapor concentration was induced fer the purpose of a quantitative analysis. The 2-D vapor/liquid images of fuel spray were captured under the evaporation condition, and the spatial distribution of vapor concentration was obtained. The spatial distribution of liquid phase had hollow-cone shape. And the vapor phase was widely distributed in the whole spray. The behavior of vapor phase was significantly affected by second flow such as entrainment, vortex, while that of liquid phase was scarcely affected.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.9-16
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• 2003

According as the industry was developed, the pollution of the environment and atmosphere rose up to the surface. So, the focus is now concentrated on the engines of affinity for nature. And the investigators make more effort to the improvement in the performance of engines, depending to the prices of oil and the anxiety about the exhaustion of the fossil fuel go up. So the GDI engines head up for these necessities. In this experimental study, the spray flow characteristics for a commercial injector equipped in the present GDI engine were investigated, which had a strong influence on the engine performance and emissions. The experiment was performed at the injection pressures of 1, 3, 5 and 7MPa under the atmospheric condition. A PDPA system was used to specify the flow characteristics of the spray. Also, the global spray behavior classified into three regions as leading, main spray and vortex cloud region, was analyzed by using a visualization system. And the regions were compared with each other.

• Journal of ILASS-Korea
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• v.12 no.1
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• pp.11-17
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• 2007

The swirl spray for direct-injection spark-ignition (DISI) engines was investigated using a nozzle whose exit surface shape was cut with a certain tapered angle. The reason for the change in spray's characteristics at various tapered angles was explained by the data correlating the taper and flow angles. The spray tended to shift its characteristics from the symmetric to asymmetric when the tapered angle was increased; furthermore, the spray penetration and spray cone angle were also increased. When the tapered angle was greater than the $90^{\circ}$ minus flow angle, an opened hollow cone spray was formed because of the fuel impingement against the tapered surface area of the nozzle exit. This behavior indicates that the reduction in the air pressure difference between the inner and outer spray of the spray can be achieved. This behavior also promises the potential use of the tapered nozzle for the case where the independence of the spray performance from atmospheric pressure and fuel temperature is desired.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.47-53
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• 2005

This paper presents the effects of ambient pressure on atomization characteristics of high-Pressure injector in a direct injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size, mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration, and global spray structure were visualized using a shadowgraph technique. In order to investigate the atomization process numerically, the LISA-DDB hybrid model was utilized. This breakup model assumes that the primary breakup occurs when the amplitude of the unstable waves is equal to the radius of the ligament of liquid sheet near the nozzle and the droplet deformation induces the secondary breakup. The results provide the effect of ambient pressure on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity distribution. It is also revealed that the accuracy of prediction of LISA-DDB hybrid model is pretty good in terms of spray developing process, spray tip penetration, and SMD distribution.

• 한국연소학회:학술대회논문집
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• 2000.12a
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• pp.194-201
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• 2000

This paper is intended to analyze the macroscopic behavior and transient atomization characteristics of the high-pressure gasoline injector in direct-injection gasoline engine. The global spray behavior of fuel injector was visualized by shadowgraph technique. Time-resolved droplet axial and radial velocity components and droplet diameter were measured at many probe positions in both axial and radial directions by a two-component phase Doppler particle analyzer (PDPA). In order to obtain the influence of fuel injection pressure, the macroscopic visualization and experiment of particle measurement on the fuel spray were investigated at 3,5 and 7 MPa of injection pressure under different surrounding pressure in the spray chamber. The results of this work show that the fuel injection pressure of gasoline injector in GDI engine has influence upon the mean droplet diameter, mean velocity of spray droplet, the spray tip penetration, and spray width under the elevated ambient pressure.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.6
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• pp.202-209
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• 1998

For development of SDI(Spark-ignited Direct Injection) engine, stratified mixture formation with adequate strength at spark plug was required in wide range of engine operating conditions. So, spray structure under high ambient pressure and spray distribution after impingement on piston bowl in motoring engine was visualized by using laser equipments. Also, incylinder bulk flow structure was measured by using PIV (Paiticle Image Velocimetry) system. Counter-rotating tumble port and bowl piston was found effective to conserve bulk motion directed to spark plug in compression stroke. In addition, mask attached near valve seat in intake port was proposed to attenuate conventional tumble component and enhance counter-rotating tumble component.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.981-987
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• 2011

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 injection timing, 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.