• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.128-136
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• 1997

Spray characteristics of a fuel injector have an important effect upon engine power and emission. Thus this study was investigated the spray characteristics of the intermittent injection using a gasoline fuel injector. Image processing system and PDA system were utilized for visualization of a spray behavior and measurements of a droplet size and velocity, respectively. Fuel injection duration was fixed with 3ms and injection pressure was varied such as 250kPa, 300kPa, 350kPa. for a high fuel injection pressure, spray tip arrival time was fluctuated at a vigorously disintegrated cross section. Axial velocity was linear correlated with fuel droplet size in the time interval of an injected main spray at spray downstream.

• Journal of ILASS-Korea
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• v.24 no.1
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• pp.1-7
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• 2019

This study was carried out to analyze the spray characteristics as a function of the operating parameters of urea injector used in Urea-SCR system of passenger diesel vehicle. Spray visualization and PDPA experiment were performed to analyze the macroscopic spray development and atomization performance of urea-water-solution. For the urea injector, the deformation of the spray head does not appear to be significant because it operates at a low pressure conditions, and the liquid core and primary droplet are observed throughout the operating conditions. No increase in atomization is seen when the operating pressure is increased, and the spray develops linearly due to poor atomization characteristics. The macroscopic spray behavior of the low-pressure urea injector is predictable through the modification of the Hiroyasu equation.

• Journal of ILASS-Korea
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• v.25 no.2
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• pp.60-67
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• 2020

Despite its benefit in engine thermal efficiency, gasoline-direct-injection (GDI) engines generate substantial particulate matter (PM) emissions compared to conventional port-fuel-injection (PFI) engines. One of the reasons for this is that the spray collapse caused by the spray-to-spray interaction forms the locally rich fuel-air mixture and increases the fuel wall film. Previous studies have investigated the spray collapse phenomenon through the macroscopic observation of spray behavior using laser optical techniques, but it is somewhat difficult to understand the interaction between sprays that is initiated in the near-nozzle region within 10 mm from the nozzle exit. In this study, the spray structure, droplet size and velocity data were obtained using an X-ray imaging technique from the near-nozzle to the downstream of the spray to investigate the spray-to-spray interaction and discuss the effects of spray collapse on local droplet size and velocity distribution. It was found that as the ambient density increases, the spray collapse was promoted due to the intensified spray-to-spray interaction, thereby increasing the local droplet size and velocity from the near-nozzle region as a result of droplet collision/coalescence.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.60-65
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• 2014

Fe-based amorphous coatings were fabricated on a soda-lime glass substrate by the vacuum kinetic spray method. The effect of the gas flow rate, which determines particle velocity, on the deposition behavior of the particle and microstructure of the resultant films was investigated. The as-fabricated microstructure of the film was studied by field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HR-TEM). Although the activation energy for transformation from the amorphous phase to crystalline phase was lowered by severe plastic deformation and particle fracturing under a high strain rate, the crystalline phases could not be found in the coating layer. Incompletely fractured and small fragments 100~300 nm in size, which are smaller than initial feedstock material, were found on the coating surface and inside of the coating. Also, some pores and voids occurred between particle-particle interfaces. In the case of brittle Fe-based amorphous alloy, particles fail in fragmentation fracture mode through initiation and propagation of the numerous small cracks rather than shear fracture mode under compressive stress. It could be deduced that amorphous alloy underwent particle fracturing in a vacuum kinetic spray process. Also, it is considered that surface energy caused by the formation of new surfaces and friction energy contributed to the bonding of fragments.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.1-6
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• 1999

An experimental study was carried out to investigate the global spray behavior and spray characteristics of high-pressure fuel injector in the direct-injection goasoline enginet. The atomization characteristics of fuel spary such as mean droplet size, mean velocity , and velocity distribution were measured by the phase Doppler particle analyzer. The spray tip penetration and spray width were investigated by the result fo visualizaiton experiment. The quantitiative spary characteristics of injector spray were measured under various sparay conditions and ambient pressures. The results of experiment show that the increase in ambient pressure have influence on the spray tip penetration and spray development process. Also, the influence of injection pressure and measuring location on the mean velocity and droplet size distribution were discussed.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.2
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• pp.181-191
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• 2002

Spray calculation has been studied to understand the behavior of the spray in a combustion chamber But the spray dispersion has not been predicted properly in a high velocity injection spray or a wall impaction spray. In this study the extended grazing collision model is applied to improve the problem. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form. The droplet distributions, penetration, width and gas flows are compared for the cases with or without extended model. The extended collision model makes the results better.

• Tribology and Lubricants
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• v.27 no.6
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• pp.351-355
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• 2011

Al/SiC composites were fabricated by thermal spray process, and the dry sliding wear tests were performed using the various sliding speed of 10, 30, 60 and 90 RPM through 1000 cycles. The applied load was 10 N and radius of wear track was 15 mm. Wear tracks on the Al/SiC composites were investigated using scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDS). In the case of sliding speed of 10 RPM, adhesive wear behavior caused by plastic deformation of composits surface was observed. In the cases of sliding speed of 30, 60, 90 RPM, abrasive wear behavior on the adhered layer formed by debris were observed. Through this study, it was found that the wear behavior of Al/SiC composites was mainly influenced by the sliding speed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.181-182
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• 2002

Most recent, Plasma ceramic spray is used on parts of tribosystem, has been investigated on the tribological performance. The application of ceramic coatings by plasma spray has become essential in tribosystems to produce better wear resistance and longer life in various conditions. The purpose of this work was to investigate the wear behavior of $8%Y_2O_3-ZrO_2$ coating due to temperatures of post-spay heat treatment. The plasma-sprayed $8%Y_2O_3--Zirconia$ coating was idiscussed to know the relationship between phase transformations and temperatures of post- spray heat treatment. Wear tests was carried out with ball on disk type on normal load of 50N, 70N and 90N under room temperature. The transformation of phase and the value of residual stress were measured by X-ray diffraction method(XRD). Tribological characteristics and wear mechanisms of coatings was observed by SEM. The tribologieal wear performance was discussed a point of view for residual stress. Consequently. post-spray heat treatment plays an important role in decreasing residual stress. Residual stress in coating system has a significant influence on the wear mechanism of coating.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.37-42
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• 2004

In a port fuel injection system of engine, a large part of fuel injected into an intake port adheres on its wall and inlet valve. Consequently, the wall impinging spray interaction might occur the generation of several harmful phenomena. There are uncontrollable mixture formation, an accidental backfire and unburned hydrocarbons. Therefore, it is important to analyze the fuel behavior during the spray-wall interaction. In this study, splash characteristics of impingement and reflecting or scattering behavior of droplets of fuel injected from EFI nozzle were studied experimentally. A test fuel used is LAWS and its physical characteristics are similar to the conventional gasoline except for the ignition point. Since the liquid film formed immediately after impinging on an impingement plate is unstable, it is easy to cause secondary disintegration. In addition, when the intermittently impingement on the impingement plate with LAWS, the splash ratio is around 0.6. If an injection period becomes longer, liquid film will become thick and the splash ratio will fall bout 10 percent. On the other hand, when the injection period of an intermittent spray is long, the same time lapse as a continuous spray is shown.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.112-120
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• 2005

The injector, which is used in a 4-valve gasoline engine, is required to be maintained the dual stream because of the design of dual intake port. In addition, the spray characteristics of fuel injector have strong influence on engine performance, exhaust emission, fuel consumption, and especially the cold start condition for the port injection. So, commercial gasoline injectors off different type were inspected. Those are 2 hole,4 hole, air shroud 4 hole, and air shroud 4 hole injector with separator. The spray behavior of dual stream was researched by the visualization system and PDPA system was employed to measure the droplet size. Atomization is one of the most important characteristic, so droplet size distributions and SMD are investigated. And the spray characteristics of each injector are also analyzed such as the spray tip penetration, spray angle, and separation angle.