• 한국자동차공학회논문집
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• 제4권5호
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• pp.187-196
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• 1996

In this study, 3-dimensional finite element model of a diesel engine cylinder head was made to accomplish heat transfer analysis and also thermal stress and deformation analysis. Heat release analysis and Nusselt-Reynolds correlations were applied to determine the convective boundary conditions which are required for heat transfer analysis to calculate temperature distribution. Thermal stress distribution was also investigated from heat transfer analysis results. Steady state temperature and heat flux were measured by using K-type thermocouples and then compared with numerical results to give a guarantee for the propriety of numerical analyses.

• 동력기계공학회지
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• 제12권6호
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• pp.64-69
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• 2008

The spatial fuel distribution of the stratified charge of a high pressure 6-hole injector was examined in a single cylinder optical direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF(Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played more effective role in the spatial fuel distribution of the stratified charge than the swirl flow during the compression stroke and the fuel distribution area increased due to the activation of the fuel vaporization by the increase of the coolant temperature. But, the increase of the fuel supplying pressure could not change the pattern of the fuel vapor distribution against the expectation.

• 한국분무공학회지
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• 제4권4호
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• pp.17-23
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• 1999

Recently, many researchers have been studied a D.I. diesel engine because of the exhaust gas restriction and fuel consumption performance. It is well known that the fuel injection characteristics are the key factors on the diesel combustion and exhaust emission. In this study, the fuel injection characteristics of 5-hole injector and the combustion characteristics are investigated with the amount of fuel by means of the visualization method and visualization D.I. diesel engine system. As the results of the experiments, the spray pattern of the fuel injection and the diffusion flame of a D.I. diesel engine are clarified. In addition, combustion phenomena with operation conditions such as engine speed and engine load are made clear.

• 한국자동차공학회논문집
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• 제7권7호
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• pp.76-85
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• 1999

GDI(Gasoline Direct Injection( engine technology is well known as a new technology since it can improve fuel consumption and meet future emission regulations. But the GDI has many difficulties to be solved, such as complexity of injection control mode, unburned hydrocarbon, and restricted power. A 2-D shape combustion chamber was adopted to investigate mixture formation and combustion characteristics of GDI engine. Spray and combustion experiments were performed by changing the injection timing. injection pressure an din-cylinder flow in Rapid Compression and Expansion Machine(RCEM).Through the experiments, the detailed characteristics of fuel spray and combustion was analyzed by visualizing the in-cylinder phenomena according to the change of injection condition, and the optimal fuel injection timing and fuel injection pressure were obtained.

• 한국자동차공학회논문집
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• 제12권2호
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• pp.24-31
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• 2004

A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyzer the heat quantity of inhomogeneous charge methane-air mixture. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. It is shown that the effect of stratification is not significant in case of the overall excess air ratio of 1.1, mainly due to the higher heat loss and lower thermal efficiency compared to those of homogeneous condition. In the case of the overall excess air ratio of 1.4, as the initial charge pressure decreases, the CHR ratio has been decreased while the HL ratio has been increased, Generally, as the initial charge pressure increases, the amount of injection mixture has been decreased and has resulted in lower mean velocity and turbulence intensity for injection mixture. Also, the injected mixture is too rich to result in mixing deficiency in combustion chamber. From these results, it could be possible to acquire the improvement of thermal efficiency and the reduction of heat loss simultaneously through the 2-stage injection in CNG direct injection engine.

• 한국자동차공학회논문집
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• 제18권6호
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• pp.145-151
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• 2010

The performance of a direct-injection diesel engine often depends on the strength of swirl or squish, the shape of combustion chamber, the number of nozzle holes, etc. This is natural because the combustion in the cylinder was affected by the mixture formation process. Since the available duration to make the mixture formation of air-fuel is very short, it is difficult to make complete mixture. Therefore, an early stage of combustion is violent, which leads to the weakness of noise and vibration. In this paper, the combustion process of a common-rail diesel engine was studied by employing two kinds of pistons. One has several grooves with inclined plane on the piston crown to generate swirl during the compression and expansion strokes in the cylinder in order to improve the atomization of fuel. The other is a toroidal piston, generally used in high speed diesel engines. To take photographs of flame and flaming duration, a four-stroke diesel engine was remodeled into a two-stroke visible single cylinder engine and a high speed video camera was used.

• 한국분무공학회지
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• 제5권4호
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• pp.57-65
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• 2000

For this research an extension of the LIF technique that the LIEF(Laser Induced Exciplex Fluorescence) technique has been used LIEF technique is the unique method to allows the visualization of fuel vapor phase and liquid phase individually by capturing each signals of them. In this work performed that the basic procedure for advanced LIEF technique using TEA and benzene as dopants md high power KrF excimer laser to excite the dopants. Iso-octane is used as the fuel because it does not absorb light at the laser wavelength. The boiling point of benzene and TEA are $81^{\circ}C\;and89^{\circ}C$, respectively, in comparison to $99^{\circ}C$ for iso-octane. It is observed that the behavior and distribution of high pressed fuel injection from various test condition. The injection pressure is set as 3MPa. and 5MPa. And the ambient pressure of test chamber is atmospheric pressure and 1MPa, the ambient temperature of chamber is room temperature, $300^{\circ}C\;and\;500^{\circ}C$ to imitate the condition of GDI engine cylinder.

• 한국분무공학회지
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• 제12권1호
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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.

• 대한기계학회논문집B
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• 제25권1호
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• pp.78-86
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• 2001

The Gasoline Direct Injection(GDI) system has been highlighted due to the improvement of fuel consumption and the control of exhaust emission from gasoline engines. The GDI system includes a high injection pressure, smaller mean diameter, good spray characteristics and stability. We were interested in the development for gasoline direct swirl injector(GDSI) in which the swirler is specially designed with an incident angle. Nymerical analysis was utilized to investigate the internal flow of GDSI with a goal to determine the swirl incident angle and needle lift. Accordingly, it describes characteristics of a GDSI in which the flowrate and spray characteristics are satisfied. especially the spray tip penetration decreases, compared with other type GDI, mean diameter of droplets is from 20${\mu}{\textrm}{m}$ to 25${\mu}{\textrm}{m}$ and spray angle ranges from 64$^{\circ}$to 66$^{\circ}$.

• 대한기계학회논문집B
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• 제31권3호
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• pp.283-291
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• 2007

The static pressure distribution, atomization characteristics and velocity distribution of tapered nozzle swirl spray is analyzed and then compared with original swirl spray. The static pressure distribution inside the swirl spray is measured using a piezoresistive pressure transducer. Phase Doppler anemometry (PDA) is applied to measure and analyze the droplet size and velocity distribution of tapered nozzle and original swirl spray. The static pressure inside the spray shows the lower value compared to the atmospheric pressure and this pressure drop is getting attenuated as the taper angle is increased. The droplet size of tapered nozzle spray shows similar value compared to the original swirl spray at the horizontal mainstream while it shows increased value at vertical mainstream. The deteriorated atomization characteristics of tapered nozzle spray is improved by applying high fuel temperature injection without causing the spray collapse. The velocity results show that the larger portion of fuel is positioned with higher injection velocity, and the smaller portion of fuel is positioned with lower injection velocity with causing spatially non-uniform mixture distribution.