• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2702-2707
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• 2007

The purpose of this study is to calculate the behavior of molecules for the generation of homogeneous thin-films in the process of spray deposition. The calculation system was composed of a suface molecular region and droplet molecular region. The thin-film was generated when droplet molecules fell to surface molecules. Lennard-Jones potential had been used as intermolecular potential, and only attraction 때 d repulsion had been used for the behavior of the droplet on the solid surface. As results, the behavior of the droplet was so much influenced by the surface temperature in the spray deposition process. High temperature of surface has higher porosity and larger spread area. It was found that simulation results generally agreed well with previous the experimental results. This simulation result will be the foundation for the deposition processes of industry.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2017년도 제48회 춘계학술대회논문집
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• pp.704-708
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• 2017

A spray characteristics is carried out in a numerical simulation of swirl coaxial injector. The water and nitrogen are the oxidizer and fuel is used in cold flow condition. The simulation is carried out in 3d model with varying recess length. Reynolds stress turbulence and volume of fluid model were chosen to perform the simulation. The spray characteristics have been investigated as well as the influence of the inlet swirl strength of the internal flow. Effect of recess length is studied for the axial and radial velocity decreased with a reduced length of inner injector due to the decline vortex intensity.

• 한국융합학회논문지
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• 제12권1호
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• pp.185-191
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• 2021

과립 분말 야금법은 기존 분말 야금법보다 치밀도가 높은 소결 부품을 얻을 수 있는 제조 기술이다. 하지만 추가 과립화 공정에 따른 생산 비용 증가가 상당하다는 단점이 있다. 과립 분말 야금법의 생산성 향상을 위해서는 과립 분말 제조 시 높은 회수율이 보장되어야 한다. 본 논문에서는 분체 동역학 전산 해석법인 이산요소법을 이용하여 과립 분말의 수율에 영향을 미치는 과립화 공정의 특성에 대해 살펴보았다. 분무 과립 공정 중 과립화 분말의 비산, 충돌 및 소착 현상을 시뮬레이션함으로써 분무 건조기의 운전 조건에 따른 과립화 분말의 파손 및 회수 가능 여부를 예측하였다. 본 논문의 가상 공정 시뮬레이션 융합 연구 결과는 실제 금속 분말의 분무 과립화 공정의 생산성 향상에 이바지할 것으로 기대한다.

• 동력기계공학회지
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• 제3권3호
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• pp.36-43
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• 1999

Many of thermodynamic-based diesel combustion simulations incorporated a model of fuel spray which attempts to describe how the spray develops according to time. Because the spray geometry is an essential aspect of the fuel-air mixing process, it is necessary to be calculated quantitatively for the purpose of heat release and emission analysis. In this paper, we proposed the calculating method of non-evaporation spray behaviors by injection rate shapes under actual operating conditions of diesel engine. We confirmed the utility of this calculating model as the calculated results were compared with the measured results. This calculating program can be applied usefully to study on the diesel spray behavior.

• 한국분무공학회지
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• 제12권4호
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• pp.191-197
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• 2007

This study presents in-line digital particle holography and its application to spray droplets to measure the characteristics of spray droplets. Several important parameters at the time of hologram recording such as the object distance and the region of laser beam used were verified. The correlation coefficient method with important parameters such as the reconstruction interval and the correlation interval was used for determination of the focal planes of particles. The optimal values of all these parameters are obtained by either numerical simulation of holograms or experiments. Using these optimal parameters, double pulse digital spray holograms in a short time interval were recorded with the synchronization system for the time control. The spatial positions of droplets that are used for the evaluation of the three dimensional droplet velocities can be easily located, which proves the feasibility of the digital holographic technology for measurements of several important features of spray droplets.

• 한국분무공학회지
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• 제15권1호
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• pp.8-16
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• 2010

This paper present the diesel spray characteristics at different injection system parameters in a HSDI diesel engine. The spray characteristics was calculated by the coupled simulation of fuel injection system model and three-dimensional KIVA-3V code with TAB spray model. The relevant injection parameters are accumulator volume, control chamber initial volume, control orifice diameter, needle valve diameter and nozzle chamber initial volume, etc. Parametric investigation with respect to twelve relevant injection parameters showed that there was a significant advantage in varying control chamber initial volume, control chamber orifice diameter, and nozzle chamber orifice diameter with respect to effect the SMD and fuel injection speed. Consequently, in order to design the fuel injection system for spray characteristics, it seems reasonable to suppose to be optimized the fuel injection system.

• 동력기계공학회지
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• 제13권6호
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• pp.13-21
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• 2009

This basic study is required to examine spray or jet behavior depending on fuel phase. In this study, analyses of diesel fuel(n-Tridecane, $C_{13}H_{28}$) spray and natural gas fuel(Methane, $CH_4$) jet under high temperature and pressure are performed by a general-purpose program, ANSYS CFX release 11.0, and the results of these are compared with experimental results of diesel fuel spray using the exciplex fluorescence method. The simulation results of diesel spray is analyzed by using the combination of Large-Eddy Simulation(LES) and Lagrangian Particle Tracking(LPT) and of a natural gas jet is analyzed by using Multi-Component Model(MCM). There are two study variables considered, that is, ambient pressure and injection pressure. In a macroscopic analysis, the higher ambient pressure is, the shorter spray or jet tip penetration is at each time after start of injection. And the higher injection pressure is, the longer spray or jet tip penetration is at each time after start of injection. When liquid fuel is injected, droplets of the fuel need some time to evaporate. However, when natural gas fuel is injected, the fuel does not need time to evaporate. Gas fuel consists of minute particles. Therefore, the gas fuel is mixed with the ambient gas more quickly at the initial time of injection than the liquid fuel is done. The experimental results also validate the usefulness of this analysis.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.59-65
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• 2004

In this paper a numerical study was performed for the effect of the wall curvature on the behaviors of fuel sprays impinging on the concave Surface. Actually, in the real diesel engines, a piston head has a curved shape for the purpose of the controlling the movement of fuel droplets and the mixture formation. For past decades, although many experimental and numerical works had been performed on the spray/wall impingement phenomena, the curvature effect of impinged wall was rarely investigated. The wall curvature affects on the behaviors of the secondary droplets generated by impingement and the concave wall obstructs the droplets to advance from the impinging site to outward. In present study, the simulation code was validated for the flat surface case and three cases of the different curvature were calculated and compared with the flat surface case for several parameters, such as the spray radius, the spray height and the position of vortex center of gas phase. The simulation results showed that the radial advance of the wall spray and the vortex is decreased with increasing the curvature. It was concluded that the curvature of the impinged wall significantly affects the behaviors of both the gas-phase and the droplet-phase.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2310-2318
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• 2004

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 400 bar to 800 bar by using a common rail injection system. Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.75-80
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• 2001

The present article deals with the numerical calculations for the inter-spray impingement of two diesel sprays under the conditions of high injection pressure. The Wave model involving the cavitation effect inside the nozzle was used for describing the atomization process. In particular, a hybrid model for drop collision was newly suggested in this study and compared with the O'Rourk's model, which has been widely used for diesel sprays. The impingement angles of 60 and 90 degrees were considered for simulation of non-evaporative diesel sprays. The calculated results for tip penetration were compared with experimental data and the Sauter Mean Diameter(SMD) characteristic was analyzed. It was concluded that the hybrid model slightly shows better agreement with experimental data than the O'Rourke's model. However, the more elaborate study should be needed for better understanding of spray-to-spray impingement phenomena.