• 한국분무공학회지
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• 제15권3호
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• pp.140-149
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• 2010

The spray-wall impingement in diesel engines is important to mixture preparation, engine performance and pollutant emissions. The purpose of this paper is to study the effects of spray-wall impingement on fuel distribution, combustion and emission characteristics by using both experimental and numerical methods. To investigate the spray-wall impingement process, an impingement-chamber was designed and a visualization experiment system was also developed. The images of impinged spray and free spray were digitally recorded with an intensified CCD camera. To investigate the fuel distribution, combustion and emission characteristics of impinged spray in a real diesel engine, the fuel injection and combustion processes of an engine with impingement-chamber were simulated by CFD software. Equivalence ratio distribution results were obtained to understand the fuel distribution characteristics of the impinged spray. Some combustion and emission characteristics were also acquired and the results showed that ignition delay of impinged spray was shorter than that of free spray; NO emission of the impinged spray was significantly less than that of free spray, but soot emission of impinged spray was more than that of the free spray. This study found that the diesel engine with spray-wall impingement has significant potential to reduce NO emission.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.7-12
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• 2005

In order to analyze the microscopic spray characteristics of free spray in ultra high pressure region, the droplets size and velocity of free spray injected under atmosphere condition were measured by PDPA. As injection pressure became ultra high pressure, the droplets size was decreased continuously due to the increase of mutual reaction between droplets and air. But the decreasing rate became moderate. The velocity was increased until 250 MPa, and then decreased over that of injection pressure. It was seemed that the droplet size was similar in range of $280\~350\;MPa$, but increased in 414 MPa, even though injection pressure was increased. The microscopic spray characteristics of free spray got worse in 414 MPa.

• 한국산업융합학회 논문집
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• 제1권2호
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• pp.41-48
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• 1998

This experimental study describes atomization characteristics of spray-spray impingement. Effect of the impingement location and angle on the penetration and the sauter mean diameter of the impinged spray were investigated. Experiment were performed under ranging from 50kPa to 250kPa spray pressure, ranging $30^{\circ}C$ to $135^{\circ}C$ angle on the penetration and free spray. In the case of this experimental, sauter mean diameter $D_{32}$ tends to decrease and duration of film disintegration $t_f$ to decrease, when spray pressure and angle on the penetration is increased. Sauter mean diameter $D_{32}$ were about 20% to be smaller compared with a free spray to jet-jet impingement and 30% to be smaller compared with a free spray to spray-spray impingement.

• Journal of Advanced Marine Engineering and Technology
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• 제24권4호
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• pp.454-459
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• 2000

Diesel engine which has high thermal efficiency is one of the major movers. Recently, as people pay attention to the environmental pollution, the emission of Diesel engine becomes an important problem. So it is needed to understand the characteristics of diesel fuel spray injected into a combustion chamber to reduce the emission. The factors which control the diesel fuel spray are the injection pressure, the nozzle diameter, the impinging angle and the variation of an ambient pressure and temperature. In this paper, the experiments were conducted in the free spray and the impinging spray with various ambient temperatures(273K, 373K, 573K). And the behaviors of the diesel fuel spray, such as penetration, spray angle and axial distance in the free spray and axial distance and spray thickness in the impinging spray were studied.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.410-415
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• 2000

A diesel engine is one of the major prime movers to its high thermal efficiency. But due to the recent attention far the environmental pollution, the emissions of diesel engine became to a important problem. So it is needed to understand the characteristics of diesel spray injected into a combustion chamber. The factor which controls the diesel spray are the injection pressure, the nozzle diameter, the impinging angle and the variation of pressure and temperature. In this paper, experiments were conducted far the variation of the environmental temperature(273k, 373k, 573k), free spray and impinging spray. And the notions of penetration, spray angle, axial distance for free spray, and axial distance, spray thickness from impinging wall fur impinging spray.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2281-2288
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• 2005

Because an injected spray development process consists of impinging and free spray in the diesel engine, it is needed to analyze the impinging spray and free spray, simultaneously, in order to study the diesel spray behavior. To dominate combustion characteristics in diesel engine is interaction between injected fuel and ambient gas, that is, process of mixture formation. Also it is very important to analyze liquid and vapor phases of injected fuel on the investigation of mixing process, respectively and simultaneously. Therefore, in this study, the behavior characteristics of the liquid phase and the vapor phase of diesel spray was studied by using exciplex fluorescence method in high temperature and injection pressure field. Finally, it can be confirmed that the distribution of vapor concentration is more uniform in the case of the high injection than in that of the low injection pressure.

• 한국분무공학회지
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• 제7권4호
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• pp.16-22
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• 2002

The characteristics of free spray with ultra injection pressure was analyzed to clear the limit pressure of diesel engine. To obtain final goal, ultra high pressure injection equipment was developed, spray patterns were visualized under various ultra injection pressures. Spray penetration and spray width, volume and entrained air mass were increased with the increase of injection pressure. Sauter mean diameter and injection durstion wert decreased. But over 3,000bar of ultra injection pressure region the rates of increase show almost similar and finally the reversed tendencies at 4,140bar.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.946-951
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• 2001

This experimental study is to investigate the intermittent spray characteristics of a pintle nozzle. High speed camera used in this expreiment with 9000fps. The factor, which controls the diesel spray, is the Injection pressure, ambient pressure and ambient temperature. In this paper, experiments were conducted free spray for the ambient pressure(3, 4, 5Mpa), nozzle Injection pressure(10, 14, 18MPa) and ambient temperature(293, 473K). With the higher opening pressure, the spray tip velocity and spray penetration increases while the spray angle decreases, On the other hand, With the higher ambient pressure, the spray angle increase while the spray tip penetration and spray tip velocity decrease. also, With the higher ambient temperature, the spray penetration decrease while the spray angle decrease.

• 한국분무공학회지
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• 제8권3호
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• pp.19-26
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• 2003

In this study, experimental study on atomization characteristics of the fuel spray impinging on the wall was at different wall distances and angles of wall inclination. The fuel injection system was composed based on the common rail system. and the injection signal was synchronized by the delay generator. The atomization characteristics of the injected spray were analyzed in terms of the SMD and velocities which were measured by using the phase Doppler particle analyzer system. It is revealed that the free spray is atomized actively above 50mm form the injector tip. In the cases of the impinged spray, the 5MD and velocity of the impinged spray are smaller than those of the free spray. The impinged spray has the maximum near the 35mm of the radial distance from the injector axis, and the atomization performance is enhanced with the decrease of the wall distance.

• Journal of Mechanical Science and Technology
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• 제19권12호
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• pp.2253-2262
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• 2005

The focus of this work is placed on the analysis of the mixture formation mechanism under the evaporative diesel spray of impinging and free conditions. As an experimental parameter, ambient gas density was selected. Effects of density variation of ambient gas on liquid and vapor-phase inside structure of evaporation diesel spray were investigated. Ambient gas density was changed between ${\rho}a=5.0\;kg/m^3$ and $12.3\;kg/m^3$. In the case of impinging spray, the spray spreading to the radial direction is larger due to the decrease of drag force of ambient gas in the case of the low density than that of the high density. On the other hand, in the case of free spray, in accordance with the increase in the ambient gas density, the liquid-phase length is getting short due to the increase in drag force of ambient gas. In order to examine the homogeneity of mixture consisted of vapor-phase fuel and ambient gas in the spray, image analysis was conducted with statistical thermodynamics based on the non-dimensional entropy (S) method. In the case of application of entropy analysis to diesel spray, the entropy value always increases. The entropy of higher ambient density is higher than that of lower ambient gas density during initial injection period.