• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.2
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• pp.23-35
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• 2003

"Backhole" is a new geometric parameter and is defined as an extra empty volume which is located behind the tangential entries at the rear part of the vortex chamber in the swirl injector. Backhole makes a difference to the spray characteristics of swirl injectors such as the spray angle, SMD, the mixing characteristics and so on. To find its characteristics, experiments are conducted by using a stroboscopic photography, a PDPA apparatus and a mechanical patternator. With the backhole, the mass flow rate of the swirl injector is increased and the center region of the injected flow has more large volume than that of without the backhole. Also the cone angle can be controlled by the backhole, so that the mixing efficiencies of swirl injectors are changed. Based on cold-flow tests, the swirl injector with the backhole may improve its performance.rformance.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.351-358
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• 2006

The capability of high pressure injection with small fuel quantify at all engine operating conditions is one of the main feature in common rail fuel injection system, which is used in small and light-duty Diesel engine. The key parameter for the better atomized fuel sprays and multiple injections of this common rail fuel injection control, that can be freely selected irrespective of the engine speed and load is the mechanism controlling the needle energizing and movement in high pressure Diesel injector. In the electro-hydraulic injector, the injection nozzle is being opened and closed by movement of the injector's needle which is balanced by pressure between the nozzle seat and the needle control chamber. This study describes the macroscopic spray structure characteristics of the common rail Diesel injectors with different electric driving method i.e. the solenoid-driven and piezo-driven type. The macroscopic spray characteristics such as spray tip speed. spray tip penetration and spray cone angle were investigated by the high speed spray, which is measured by the back diffusion light illumination method with optical system for the high speed temporal photography in a constant volume chamber pressurized by nitrogen gas. As the results, the prototype piezo-driven injector system was designed and fabricated for the first time in domestic case and the effect of injector's needle response driven by different drive type was compared between the solenoid and piezo-driven injector It was found therefore. that the piezo-driven injector showed faster needle response and had better needle control capability by altering the electric input value than the solenoid-driven injector.

• Journal of ILASS-Korea
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• v.10 no.3
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• pp.17-28
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• 2005

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. In this study, diffused illumination holographic system to measure the sizes and 3D velocities of moving particles based on automatic image processing was developed. First of all basic optical systems for pulse laser recording, continuous laser reconstruction, and image acquisition, were constructed. To determine the position of particles in the optical axis, new three auto-focusing parameters(AEP), namely, Correlation Coefficient, Sharpness Index, and Depth Intensity were introduced and verified. The developed system was applied to spray droplets to validate the capability of the system. Three dimensional positions of particles viewed from two sides were decided using AFP and then 3D velocities of Particles were extracted by particle tracking algorithm. Comparison of measurement results of sizes and 3D velocities of particles with those obtained by laser instrument, PDPA, showed good consistency of the developed holographic system.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.841-844
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• 2006

Recently, tunnels being constructed in korea with the increased construction of highways, high-speed railways and hydro structure. shotcrete and spray is one of the major processes in that construction. So general Shotcrete and spray has many problems on strength property, environmental pollution and human body noxiousness as the use of accelerater. However, In this paper using HES-LMS(High Early Strength Latex Modified Spray) without accelerater can solve problems which are mentioned above. problems that the hish early cement has can be solved by modifying material with latex. Therefore HES-LMS mortar is Classify by High performance and High ability. Analysis according to the variables such as W/C, Latex content and sand content is conducted. Studied about mechanical characteristic of material such as each parameter characteristic, and rebound characteristic is completed.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.56-57
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• 2006

Porosity in spray-formed materials is an important issue, but the formation of porosity is not completely understood. The paper gives some examples picked from literature, which show some general correlations between process parameters and porosity. To improve the understanding of porosity formation it is necessary to know more about the conditions of the droplets and the deposit at the point of impingement. Determining the impact conditions is a challenge because usually they are not constant with time and some values are difficult to measure. Our experiments show a strong correlation between the deposit surface temperature and the porosity. The average impact angle weighted by the local particle mass flux is also an important parameter.

• Journal of the Korean institute of surface engineering
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• v.33 no.5
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• pp.329-338
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• 2000

In this study, as an effort to improve the brittlement of coating layer, aluminum bronze coatings formed on steel substrates by arc jet spray process were subjected to post heat treatment. After each treatment, mechanical properties such as hardness, and UTS, and microstructural characterization of the specimens were investigated. The results showed that the hardness in the coatings slightly decreased with increasing heat treatment tine and temperature. The UTS of as-sprayed coatings was 4.31kgf/$\textrm{mm}^2$ and slightly increased to 5.51kgf/$\textrm{mm}^2$ after heat treatment at $900^{\circ}C$ for 120min. On the other hand, the interdiffusion of copper and aluminum particles after heat treatment lead to decrease of the porosity density and increase the bond strength.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.69-75
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• 2003

In this study, his technique was applied to a GDI spray in order to investigate the mixture distribution. In addition, the homogeneity degree and diffusion effect according to ambient temperature in the high pressure chamber were analyzed by using an entropy analysis method. From this experiment, we could find that entropy analysis is very effective method for the analysis of mixture formation, and the entropy values increase with the progress of uniformity in diffusion Process. we tried to provide the fundamental data for parameter which effects on the spray macroscopic characteristics with mixture ratio of diesel and gasoline. In addition, the mixture formation was analyzed by using entropy analysis. The entropy analysis is based on the concept of statistical entropy, and it identifies the degree of homogeneity in the fuel concentration. From the entropy analysis results we could find that the direct diffusion phenomena is a dominant factor in the formation of a homogeneous mixture at downstream of GDI spray especially in vaporizing conditions. As to increasing ambient temperature and increasing gasoline rate, the entropy intensity using the statistic thermodynamics method is increased because evaporation rate is higher gasoline than diesel.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.628-634
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• 2016

The 8 wt% yttria($Y_2O_3$) stabilized zirconia ($ZrO_2$), 8YSZ, a typical thermal barrier coating (TBC) for turbine systems, was fabricated under different starting powder conditions and coating parameters by atmospheric plasma spray (APS) coating process. Four different starting powders were prepared by conventional spray dry method with different additive and process parameter conditions. As a result, large- and small-size spherical-type particles and Donut-type particles were obtained. Dense structure of 8YSZ coating was produced when small size spherical-type or Donut-type particles were used. On the other hand, 8YSZ coating with a porous structure was formed from large-size spherical-type particles. Furthermore, a segmented coating structure with vertical cracks was observed after post heat treatment on the surface of dense structured coating by argon plasma flame at an appropriate gun distance and power condition.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.636-642
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• 2014

As environment problem became a worldwide issue, countries are tightening regulations regarding greenhouse gas reduction and improvement of air pollution problems. With these circumstances, one of the renewable energies produced from biomass is getting attention. Bio-ethanol, which is applicable to SI engine, showed a positive effect on the PFI (Port Fuel Injection) type. However, Ethanol has a problem in homogeneous mixture formation because it has high latent heat of vaporization characteristics and in the GDI (Gasoline Direct Injection) type, mixture formation is required quickly after fuel injection. Particularly, South Korea is one of the countries with great temperature variation among seasons. With this reason, South Korea supply fuel additive for smooth engine operation during winter. Therefore, experimental study and investigation about application possibility of blending fuel is necessary. This paper demonstrates the spray characteristics by using the CVC direct injection and setting the bio-ethanol blending fuel temperature close to the temperature during each seasons: -7, 25, $35^{\circ}C$. The diameter and the width of the CVC are 86mm and 39mm. High-pressure fuel supply system was used for target injection pressure. High-speed camera was used for spray visualization. The experiment was conducted by setting the injection pressure and ambient pressure according to each temperature of bio-ethanol blending fuel as a parameter. The result of spray visualization experiment demonstrates that as the temperature of the fuel is lower, the atomization quality is lower, and this increase spray penetration and make mixture formation difficult. Injection strategy according to fuel temperature and bio-ethanol blending rate is needed for improving characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.406-406
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• 2011

결정질 태양전지에서 도핑(Doping)은 반도체(Semiconductor)의 PN 접합(Junction)을 형성하는 중요한 역할을 한다. 도핑은 반도체에 불순물(Dopant)을 주입하는 공정으로 고온에서 진행되며 온도는 중요한 변수(Parameter)로 작용한다. 본 연구에서는 여러 가지 에미터(emitter)층 형성방법 중에 가장 저가이면서 공정과정이 간단하며 대면적 도핑이 용의한 Spray 방법을 통해 효과적인 에미터 층 형성의 최적화를 위해 DI water에 각각 1%, 3%, 5% 7%로 희석된 H3PO4용액 으로 850$^{\circ}C$에서 열처리 시간을 가변해 가며 최적화된 면저항과 표면농도 특성을 분석하였다. 도핑소스가 웨이퍼(wafer) 각각의 표면에 흡착시킨 후 오븐에 넣어 150$^{\circ}C$에서 5분간 건조시킨 후 퍼니스(furance)에 넣어 시간을 가변해 가며 도핑시켰다. Spray 방식은 기존의 방식보다 저렴하고 In-line 공정에 적합하며 대용량으로 전환이 쉽다는 많은 장점을 가지고 있다. 도핑시 먼저 spray를 이용하여 웨이퍼 표면에 균일하게 용액을 흡착시킨 후 오븐에서 150$^{\circ}C$에서 5분간 건조 후 furnace에 넣어 850$^{\circ}C$에서 시간을 가변 해가며 실험하였다. H3PO4용액의 비율이 1%일 때는 2분 이상 열처리를 하였을 때 60${\Omega}/{\Box}$ 이하로 내려가지 않았다. 이는 최초 표면농도가 낮아 더 이상 확산되지 않음을 의미한다. 또한 H3PO4의 비율이 3% 이상일 때는 열처리 시간이 1분 이하일 때 면저항의 변화가 거의 없었으나 2분 이상일 때는 시간에 따라서 점차 낮아졌으며 균일도 역시 좋아졌다. 이는 H3PO4의 비율이 3% 이상일 때는 표면농도가 높아서 1분 이하의 열처리 시간에서는 확산해 들어가는 양이 거의 같음을 알 수 있었다.