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Park, Junkyu,Kim, Taehoon,Kim, Donghwan,Park, Sungwook Elsevier 2018 Fuel processing technology Vol.179 No.-
<P><B>Abstract</B></P> <P>This study was performed to analyze the wall impingement and fuel film formation in a DISI engine with injection strategies using image-based analysis and CFD. The direct injection engine uses a high-pressure injection strategy to improve the homogeneity of the air-fuel mixture, so the spray behavior was analyzed by spray visualization for various injection pressures, and the wall impingement was predicted for various engine operating conditions based on the acquired images. The mass distribution of the injected fuel was calculated using the injection profiles and the spray image, and the amount of fuel that impinges on the piston and wall (i.e., the geometric boundaries of the cylinder) was calculated using data from the spray behavior for various engine operation conditions such as load and engine speed. The image-based analysis was limited to understanding the influence of the injection strategy on the droplet behavior after wall impingement of the fuel spray. Therefore, CFD using KIVA 3 V code was additionally conducted to analyze the effects of the injection strategies on wall film formation and droplet rebounding reflecting in-cylinder conditions. In the early- and late-injection conditions, the initial piston position is high, and most of the injected fuel impinges on the piston. As the injection pressure increases, the injection timing at which wall impingement occurs is advanced because of the rapid spray development. The results of the 3D analysis for the temperature and the intake flow in the engine cylinder showed that both the wall impingement and the fuel film were reduced as the injection pressure increased because the fuel evaporation increased due to improved atomization.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A prediction method of wall impingement in DISI engines is introduced. </LI> <LI> Effects of injection pressure and injection timing on spray wall impingement are analyzed using image-based method. </LI> <LI> 3D CFD are used to analyze effects of the engine conditions on formation of fuel film. </LI> <LI> Higher injection pressure conditions can reduce formation of fuel film due to superior vaporization characteristics. </LI> </UL> </P>
( Junkyu Park ),( Donghwan Kim ),( Hyuckmo Kwon ),( Joonkyu Lee ),( Soohong Lee ),( Sungwook Park ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
This paper describes effects of nozzle design parameters including number of nozzle hole, spray angle, and HFR on nozzle flow and spray characteristics. Injection profiles were measured using Bosch method in order to analyze flowrate depending on the nozzle design parameters and spray visualization was performed under various injector driving conditions to compare the macroscopic spray behavior in terms of the spray tip penetration and the spray cone angle. The experimental results were validated against through the Hiroyasu equation after modifying adjustable constants to fit to high pressure injection region. The flowrate was proportional to the size of HFR, which means the static flow at 100 bar. Under various injection pressure, flowrate was proportional to square root of increment of injection pressure and corresponded well to the predicted formula based on the Bernoulli equation. As number of nozzle holes increased under fixed total flow rate condition, the slower spray development was observed due to reduced nozzle outlet diameter, and the spray cone angle was similar for the cases of various nozzle diameter. For nozzle condition in which the spray angle was changed from the reference (153°), there was no significant difference in terms of macroscopic spray characteristics, but the emission characteristics can be deteriorated due to differences in air entrainment in the cylinder.
Junkyu Park,Donghwan Kim,Sungwook Park 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.3
This study was performed to investigate the effects of L/D ratio of the nozzle on initial development and macroscopic spray behavior of diesel spray to understand the formation process of spray cone angle. Near-field and far-field spray visualization was performed for various injection pressures, and the effects of L/D ratio of the nozzle on spray cone angle were analyzed. A long-distance microscope and a CCD camera were used to obtain near-field spray images. Also, macroscopic spray development was evaluated using a high-speed camera and two metal halide lamps to compare the spray cone angle depending on L/D ratio. In the initial stage of injection, a laminar flow regime is observed, and downstream of the liquid column is deformed due to the large drag force of the surrounding gas. The area of the initial spray head, which has a small amount of momentum, becomes wider due to drag, and a strong eddy flow is formed around the deformed spray head. As the momentum of the supplied fuel increases over time, a mushroom-like structure is formed because momentum is continuously supplied at the center of the spray, while the outside of the spray head receives only drag force without providing additional momentum.
리튬 이차전지 양극재 LixV2O5 의 효율적인 방전을 위한 구조 설계
박준규(Junkyu Park),김수일(Sooil Kim),김동철(Kimdong chul) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
Recently, a need for higher capacity and energy density for enhancing performance of lithium ion battery is increasingly demanded with commercial distributions of electric and hybrid vehicles. Computational analysis was performed on a porous structure of vanadium pentoxide cathode employing phase field model. An incipient model as a spherical structure with pores, which has a cylindrical shape, was designed. Modifying diameters and lengths of pore cylinder and the number of porous, we considered different conditions of porous vanadium pentoxide cathodes in order to analyze the effect on an amount of intercalated lithium ion to the cathodes. Then we optimized the porous structure to contain the largest amount of intercalated lithium ion during discharge.
박준규 ( Junkyu Park ) 한국서양사연구회 2017 서양사연구 Vol.0 No.56
This thesis examines the development of relationship between Frankish Kingdom and church in the reign of Pepin the Short. Scholars who did research history of Early Middle Ages have paid considerable attention to interrelationship between temporal power and religious power. The earlier studies have pointed out detailed aspect under the premise that Kingdom and church already formed close contact. This existing perspective, however, neglects reign of Pepin which lay the foundation of change. The cause and background of premise have not been fully examined. Charles Martel dealt with chuch with a high hand. On the other hand Charlemagne respected church. This change was possible because of Pepin’s effort for bringing church over to his party. To illuminate Pepin’s effort, this thesis scrutinizes chronicles and the saint’s lives. This process is tied up with Boniface’s whereabouts. Boniface was a key figure when the reform of Frankish Church was being made. He not only tried to introduce hierarchy to Frankish Church, but also strove to get rid of interference of worldly person to the administration of the church. His effort was reflected in the edict of the Church synod, Concilium Germanicum. But after Carloman was driven out from the mayorship, Pepin took lead in the reform of the church. He was not so much a follower of Boniface as arbitrary user. Capitulary issued in 747 and the event of incorporation of Fulda Monastery into Royal abbey show Pepin’s unique policy. To research How Pepin tried to form a relationship between temporal power and religious power provide clue to understanding of Early Middle Ages. (Seoul National University/shakuntara@naver.com)