• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.10
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• pp.1285-1293
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• 2000

In port fuel injection system of SI engines, injected fuel is impinged onto the surface of intake valves and port-wall, and then formed the wall flow under the cold start operation. Wall flows entrained into the cylinder result in the unsteady and nonuniform mixture formation. Therefore, the spray impingement to the wall is considered as having negative influences such as lowering combustion efficiency and causing unburned hydrocarbon emissions. This study investigates the spray characteristics of the wall impinging air-assist spray in suction air flow. A PDPA was used to analyze the flow characteristics under the different conditions such as impingement angle and supplied air. Experimental data concerning the impinging sprays has been obtained in the vicinity of the wall. Measured droplets divided into the pre-impinging droplets which denote as the positive normal velocities and post-impinging droplets that describe as the negative normal velocities for the suction flow. Their velocities, size distributions and SMD are comparatively analyzed before and after the impingement.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.58-64
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• 1998

In the gasoline engine of fuel injection type, atomization of fuel droplet and its distribution has directly influenced the performance of engine and harmful emission. To investigate atomization characteristics of fuel spray, in this paper fuel spray of air-assisted injector is observed at the various initial conditions of ambient air temperature and air assisted pressure. Behavior of fuel spray is photographed with microscopic visualization system. The SMD of fuel droplet is measured with PMAS (Particle Motion Analysis System). The effect of air-assisted pressure and temperature of ambient air resulted in the decrement of SMD and its variation. Finally, It was found that It was found that from spray angle at the two-hole injector had measured $20{\pm}4$ degree the result of photographs by shadow graphy. The mean diameter of suns decreased and the of droplets increased with increasing the temperature in the spray fields by the results of PMAS measurement. It was found that the characteristics of sprays became finer by increasing the temperature of spray fields about 373K without the delivery of air-assistance.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.434-440
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• 2000

The atomization characteristics of air-assist atomizer which is surrounded by a coflowing airstream is investigated. The air-assist, coflow air stream had swirl imparted to them in the same direction with 45 degree's angle swillers. The fuel and air entered the combustor at ambient temperature and the combustor was operated in an unconfined environment. Diesel fuel was used for all the experiments. Drop size and mean velocity are reported for certain distances downstream from the nozzle. The droplet size and velocity measurements were performed using a two-component phase/Doppler particle analyzer and velocity profiles across the entire flowfield are presented.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.65-76
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• 1998

An experimental and numerical study of a spray flow is performed to investigate the spray characteristics using an air-assisted atomizer. A Partical Dynamic Analyzer(PDA) is used to measure SMD, dmp velocity, and drop number density whose the initial conditions have considerable effect on the numerical results. The measured experimental data have been used to asses the accuracy of model predictions. Numerical investigation is made with the Eulerian - Lagrangian formulism. Turbulent dispersion effects using a Monte-Carlo method, turbulent modulation effect and entrainment of air are also numerically simulated. Results show that the numerical predictions of SSF(Stochastic Separated Flow) analysis yielded reasonable agreement with the experimental data. However, the model calculations for small drops produced the inconsistent numerical results due to the effect of surrounding air entrainment.

• Journal of ILASS-Korea
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• v.3 no.4
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• pp.16-24
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• 1998

The fuel injection type, in the gasoline engines of atomization of fuel droplet and its distribution hae influenced directly on the decision of engine performance and harmful emission. In this paper, atomization characteristics of fuel spray is investigated with microscopic visualization system. Particle motion analysis system is used to measure the SMD from fuel spray of air-assisted injector by initial factors such as temperature of ambient air and air-assisted pressure. As air-assist pressure and ambientair temperature increase, the SMD is decreased, and its variation is more stable.

• Journal of ILASS-Korea
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• v.13 no.3
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• pp.126-133
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• 2008

The atomization characteristics of the dual air supplying two-fluid nozzle were investigated experimentally using PIV and PDA systems. The twin-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air, and the main nozzle to produce sprays. The main nozzle has the swirler with four equally spaced tangential slots, which gives the injecting fluid an angular momentum. The swirl angle in the swirler varied with $0^{\circ}$, $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$. The ratios of carrier air to assist air and ALR (total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the AMD and SMD distributions of the sprays were measured using PDA system. As a result, the SMD distribution increases along the radial distance, and it decreases with the increase of swirl angle in swirler.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.5
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• pp.88-96
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• 2017

As a part of the development procedures of scramjet engine with a regenerative cooling system, this experiment was performed using air-assist type injectors for scramjet engine. Two types of injectors were used in this experiment with the 90 and 60 degrees of the injection angle to the main flow. Mie-scattering was used for spray visualization and PDPA was used for the measurement of the atomization characteristics. It was found that increasing the pressure of supplied gas and the distance from nozzle tip led to the enhancement atomization characteristics and the injector with 60 degrees injection angle has better atomization characteristics than 90 degrees injector.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.54-60
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• 2008

The atomization characteristics of the dual air supplying twin-fluid nozzle were investigated experimentally using PIV and PDA systems. The two-fluid nozzle is composed of three main parts: the feeding injector to supply fluid that is controlled by a PWM (pulse-width modulation) mode, the adaptor as a device with the ports for supplying the carrier and assist air and the main nozzle to produce the spray. The main nozzle has the swirl tip with four equally spaced tangential slots, which give the injecting fluid an angular momentum. The angle of the swirl tip varied with 0$^{\circ}$ 30$^{\circ}$, 60$^{\circ}$ and 90$^{\circ}$, and the ratios of carrier air to assist air and ALR(total air to liquid) were 0.55 and 1.23, respectively. The macroscopic behavior of the spray was investigated using PIV system, and the mean velocity, turbulent intensity and SMD distributions of the sprays were measured using PDA system. As the results, the mean axial velocity at the spray centerline decrease with the increase of the swirl angle. The turbulent intensities of the axial and radial velocity were increased with the increase of the swirl angle. The mean SMD (Sauter mean diameter) of the radial direction along the axial distance shows the lowest value at the swirl angle of 60$^{\circ}$.

• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1131-1142
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• 2000

In an effort to illustrate the global variation of SMD (Sauter mean diameter, or $D_{32}$) and AMD (Arithmetic mean diameter, or $D_{10}$) at five axial downstream locations (i. e., at Z=30, 50, 80, 120, and 170 mm) under the different experimental conditions, the radial coordinate is normalized by the spray half-width. Experimental data to analyze the atomization characteristics concerning with an internal mixing type have been obtained using a PDPA(Phase Doppler Particle Analyzer). The air injection pressure was varied from 40 kPa to 120 kPa. In this study, counterflowing internal mixing nozzles manufactured at an angle of $15^{\circ}$with axi-symmetric tangential-drilled four holes have been considered. By comparing the results, it is clearly possible to discern the effects of increasing air pressure, suggesting that the disintegration process is enhanced and finer spray droplets can be obtained under higher air assist. The variations in $D_{32}$ are attributed to the characteristic feature of internal mixing nozzle in which the droplets are preferentially ejected downward with strong axial momentum, and dispersed with the larger droplets which are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup by higher shear stresses at farther axial locations. The poor atomization around the centre close to the nozzle exit is attributed to the fact that the relatively lower rates of spherical particles are detected and these drops are not subject to instantaneous breakup in spite of the strong axial momentum. However, substantial increases in SMD from the central part toward the edge of the spray as they go farther downstream are mainly due to the fact that the relative velocity of droplet is too low to cause any subsequent disintegration.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.27-27
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• 1999

To illustrate the global variation of the droplet mean diameters and the turbulent flow characteristics in counterflowing internal mixing pneumatic nozzle, the experimental measurements at five axial downstream locations(i.e., at Z=30, 50, 80, 120, and 170mm) were made using a PDPA(Phase Doppler Particle Analyzer) under the different air injection pressures ranging from 40 ㎪ to 120 ㎪. A nozzle with axi-symmetric tangential-drilled four holes at an angle of 15$^{\circ}$ has been designed and manufactured. The distributions of velocities, turbulence intensities, turbulence kinetic energy, turbulent correlation coefficients, spray angle, droplet mean diameters, volume flux, number density are quantitatively analyzed. It is possible to discern the effects of increasing air pressure. It indicates that the strong axial momentum in spite of more or less disparity between the velocity components means more reluctant to disperse radially, and that axial fluctuating velocities are substantially higher than those of radial and tangential ones, suggesting that the disintegration process is enhanced under higher air assist. The larger droplets are detected in the spray centerline at the near stations and smaller ones are generated due to further subsequent breakup at farther axial locations are attributed to the internal mixing type nozzle characteristics. Despite of the strong axial momentum, the poor atomization around the centre close to the nozzle exit is attributed to the lower rates of spherical particles which are not subject to instantaneous breakup. As it goes downstream, however, substantial increases in SMD(Sauter Mean Diameter) from the central part toward spray periphery are understandable because the droplet relative velocity is too low to bring about any subsequent disintegration.