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스로틀링을 이용한 T 형 미소 채널에서의 혼합에 관한 수치 해석적 연구
장지환(Jihwan Jang),이도형(Dohyung Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
Mixing in Y-channel micro mixer is analyzed through computational fluid dynamics. In the case of passive mixing, we investigate the effect of geometric parameters on the mixing efficiency, such as shape of throttling geometry and angle between two inlets. Mixing performance improves as two fluids join not just horizontally but both vertically and horizontally, and it also improves when channel follows throttling shapes. A numerical results substantiate the highly efficient mixing performance. It is highly beneficial to fabrication process since the proposed throttling geometry is simple, but allows high mixing ratio.
직분사가솔린엔진에서의 초고압 연료분사시스템 적용에 따른 연소 및 배기 특성
장지환(Jihwan Jang),박정환(Jeonghwan Park),김지석(Jiseok Kim),유영수(Youngsoo Yu),박성욱(Sungwook Park),김형익(Hyungik Kim) 한국자동차공학회 2022 한국 자동차공학회논문집 Vol.30 No.2
In this study, in an attempt to analyze the effect on combustion and the exhaust characteristics of the ultra-high pressure fuel injection system in the gasoline direct injection(GDI) engine, the conventional fuel injection pressure of 350 bar and the 500 bar fuel injection system were compared. To improve the delay of the needle behavior due to the fuel pressure of 500 bar, a non-magnetic ring was inserted so that magnetic force loss would not occur, unlike the low-pass method of a magnetic force transfer of the existing injector. In the process of engine evaluation, indicated mean effective pressure(IMEP) and brake specific fuel consumption(BSFC) results based on load were compared, while combustion speed and loss were calculated by additionally measuring engine combustion pressure. As a result, in terms of combustion speed and loss, the 350 bar system showed better results under the low load condition, but, as the load increased, the 500 bar system showed faster combustion speed and less loss. Lastly, in the case of exhaust gas emission characteristics, when the exhaust results for the 350 bar and 500 bar fuel injection systems were compared, NOx emission showed a higher emission at the 500 bar condition, compared to the 350 bar, as the load condition increased. Conversely, in the case of CO emission, lower emission could be confirmed at 500 bar condition as the load condition increases. This result can be considered as influencing combustion temperature according to the combustion rate. Furthermore, in the results of particle number(PN) emission, high PN reduction was confirmed by the application of an ultra-high pressure injection.
CFD 를 이용한 CMP 의 Groove Sizing 최적화
장지환(Jihwan Jang),이도형(Dohyung Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.11
In this paper, slurry fluid motion, abrasive particle motion, and effects of groove sizing on the pads are numerically investigated in the 2D geometry. Groove depth is optimized in order to maximized the abrasive effect. The simulation results are analyzed in terms of shear stress on pad, groove and wafer, streamline and velocity vector. The change of groove depth entails vortex pattern change, and consequently affects material removal rate. Numerical analysis is very helpful for disclosing polishing mechanism and local physics.