• 한국항공우주학회지
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• 제35권2호
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• pp.136-142
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• 2007

본 연구에서는 초음속 충동형 터빈의 유동특성을 알아보기 위해 소형 초음속 풍동을 설계하였다. 실험은 2차원 초음속 노즐과 익렬을 조합하여 터빈 설계 인자 중의 하나인 터빈 축 간격비에 따라 실시하였으며 단일경로 슐리렌(Schlieren) 시스템을 이용하여 유동을 가시화하였다. 그리고 다채널 압력측정 시스템을 이용하여 터빈 익렬 내의 정압력과 전압력을 측정하였다. 이러한 실험을 통해 충격파를 포함한 복잡한 유동 형태와 유동박리, 충격파-경계층 상호작용 등을 관찰할 수 있었다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.190-190
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• 1999

CHF (Critical heat flux) on the external surface of the reactor vessel lower head is major key in the evaluation on the feasibility of IVR-EVC (In-Vessel Retention through External Vessel Cooling) concept. To identify the CHF on the external surface, considerable works have been performed. Through the review on the previous works related to the CHF on the external surface, liquid subcooling, induced flow along the external surface, ICI (In-Core Instrument) nozzle and minimum gap are identified as major parameters. According to the present analysis, the effects of the ICI nozzle and minimum gap on CHF are pronounced at the upstream of test vessel: on the other hand, the induced flow considerably affects the CHF at downstream of test vessel. In addition, the subcooling effect is shown at all of test vessel, and decreases with the increase in the elevation of test vessel. In the real application of the IVR-EVC concept, vertical position is known as a limiting position, at which thermal margin is the minimum. So, it is very important to precisely predict the CHF at vertical position in a viewpoint of gaining more thermal margins. However, the effects of the liquid subcooling and induced flow do not seem to be adequately included in the CHF correlations suggested by previous works, especially at the downstream positions.

• 대한기계학회논문집B
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• 제38권3호
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• pp.235-242
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• 2014

공기 베어링의 성능개선을 위하여, 일반적인 급기공 형상(drill shape), 곡면 급기공 형상(matched cube shape) 및 $45^{\circ}C$ 모따기 노즐 출구부(trimmed shape)를 가지는 3가지 형태의 노즐형상에서 급기압을 변화 시켰을 때, 샤프트면 출구압력 특성을 전산유체역학 상용코드를 이용하여 분석하였다. 샤프트면 에서 압력 분포는 노즐 중심부에서 정체점 유동의 영향으로 최대압이 발생하며, 노즐 출구부와 샤프트면 사이의 압력분포는 미세 간극의 영향으로 와류가 형성되어 반경방향으로 국부적인 압력상승 현상이 발생한 후 음압영역이 발생하는 것이 관찰되었다. 또한 이러한 현상은 일반적인 형태의 노즐에서 급기압력비 6.92이상인 경우는 나타나지 않는 것으로 관찰되었다. 급기공 노즐 형상을 matched cubic 곡면으로 변화시켜 샤프트면에서 얻어진 압력 분포는 기존의 노즐과 비교한 결과 순간적인 상승압 구간이 모든 경우에 대하여 존재하였으며 급기압력비 10근처까지 음압구간이 나타나는 것으로 관찰되었다. 또한, 노즐 출구부를 모따기로 변형시켰을 때, 샤프트면에서 최대압력의 영향권이 반경방향으로 확대되었고 음압영역은 나타나지 않는 것으로 관찰되었다. 결과적으로, 급기공 내부의 형상변화보다는 노즐 출구면 외부의 변형이 성능개선에 유리한 것으로 관찰된다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.342-348
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• 2002

The welding technology for production of power plant facility as for other industries has been progressing forward automation and mechanization for cost reduction and shortening of cycle time. The welding for boiler tube is automated or mechanized as the parts and subassemblies of tubes are conveyed automatically in the shop. The temperature of boiler stearn is being progressively increased for higher plant efficiency. The welding of nuclear component is characterized by heavy thickness and narrow gap Submerged Arc Welding. Narrow gap Gas Metal Arc Welding and Electron Beam Welding is applied to turbine diaphragm. To improve the resistance of solid particle erosion of turbine blade and nozzle partition, HVOF spray technology and boriding process has been applied.

• 한국정밀공학회지
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• 제31권6호
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• pp.491-495
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• 2014

We developed a compact high-precision slot-die coating machine for thin-film deposition on a flexible substrate. For smooth and precise coating, air-bearing and linear motor system were employed to minimize velocity ripple. The gap control mechanism is specially designed to have repeatability of gap between nozzle and substrate under 1 ${\mu}m$. Due to extremely precise gap control, the machine can coat thin-films down to 50 nm with $200mm{\times}100mm$ size. A thin film of Ag nano-particle ink is coated for demonstration.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1536-1537
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• 2011

The high-voltage circuit breaker plays an important role in the electrical system because there has been a need for suitable switching devices capable of initiating and interrupting the flow of the electric fault current. It continues as the contacts recede from each other and as the newly created gap is bridged by a plasma. The arc plasma happens inside the insulation nozzle of SF6 self-blast interrupter which is newly developed as the next-generation switching principle. The ablation of PTFE nozzle is caused by this high temperature medium, the PTFE vapor from the nozzle surfaces flows toward the outlets and the pressure chamber. The vapor makes the pressure of the chamber increased by heat and mass transfer from the arcing zone. Because the rate of ablation depends on the magnitude of applied current, it decreases when the current goes to zero. The compressed gas inside the chamber flows reversely toward the arc plasma during this moment. According to this principle, the arc can be cooled down and the fault current can be interrupted successfully. In this study, we calculate arc plasmas and thermal-flow characteristics caused by fault current interruption inside a SF6 self-blast interrupter, and to investigate the effect of PTFE ablation on the whole arcing history.

• 한국인쇄학회지
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• 제28권1호
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• pp.51-63
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• 2010

Ink-jet is part of the non impact printing that shooting the ink drop from the nozzle to paper. It is very silence and express good color. There are two types of printing that continuous and drop on demand. But drop on demand process is becoming the mainstream. these days, LCD, PDP is passed more than semiconductor industry. And we expect organic EL, FED as a next display. But product equipment, main component and technology have a gap between an advanced country and us nevertheless physical development. Expecially, previous process part is depended on imports. Ink-jet printing technology that there isn't complicated photo lithography process is attracted, so ink-jet printing resolution is more embossed. But there were not many of ink-jet resolution thesis but ink-jet head or nozzle. Because, to out of the ink from the nozzle is unseeable and hard to experiment. Therefore this thesis was experimented and simulated how can ink-jet printer improved resolution by flow-3d simulation package program.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.100-105
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• 2005

본 연구에서는 초음속 충동형 터빈의 유동특성을 알아보기 위해 소형 초음속 풍동을 설계하였으며 Single pass Schlieren system을 이용하여 유동을 가시화하였다. 실험은 2차원 초음속 노즐과 익렬을 조합하여 노즐-익렬 간극에 따라 실시하였다. 실험을 통해 유동을 가시화하고 익렬 내부의 압력을 측정하였다. 그리고 이를 통해 충격파를 포함한 복잡한 유동 형태와 노즐-익렬, 충격파-경계층 상호작용 등, 초음속 충동형 터빈의 유동측성을 관찰할 수 있었다.

• Nuclear Engineering and Technology
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• 제41권3호
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• pp.287-294
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• 2009

Due to thermal hydraulics phenomena, such as thermal stratification, various events occur to the parts of a nuclear power plant during their lifetimes: e.g. cracked and dislocated pipes and thermally fatigued, bent, and damaged supports. Due to the operational characteristics of the parts of the steam generator feedwater inlet horizontal pipe, thermal stratification takes place particularly frequently. However, the thermal stress due to thermal stratification at the steam generator feedwater inlet horizontal pipe was not reflected in the design stage of old plants(Kori Unit No.1, 2, 3 and 4, Yeonggwang Unit No. 1 and 2, and Uljin Unit No. 1 and 2; referred to as old-style power plants hereinafter). Accordingly, a verification experiment was performed for thermal stratification in the horizontal inlet nozzle steam generator of old-style plants. If thermal stratification occurred in the horizontal pipe of an old-style power plant, numerical analysis of the temperature distribution of the pipes and fluids was conducted. The temperature distributions were compared at the curved part of the pipe and the horizontal pipe before and after the installation of the improved thermal sleeves designed to alleviate thermal stress due to thermal stratification. The thermal stress reduction measure was proven effective at the steam generator inlet horizontal pipe and the curved part of the pipe.

• 항공우주시스템공학회지
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• 제8권1호
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• pp.30-35
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• 2014

This study has been conducted to develop an ejector system applied in the aircraft engine-bay ventilation system. Tandem-Ejector was selected as a component of ventilation system because it could achieve high ventilation performance in spite of motive flow with small flow rate. Tandem-Ejector is composed of a primary nozzle and two mixing ducts ($1^{st}$ mixing duct and $2^{nd}$ mixing duct). In this study, 1-D Tandem-Ejector model has been built with conservation laws and isentropic relation for 1-D ejector sizing and performance prediction. Computational Fluid Dynamics(CFD) has been conducted to investigate ejector performance and flow characteristics in the ejector. Also, Tandem-Ejector performance tests have been conducted to obtain ejector pumping performance and to investigate stand-off (gap between primary nozzle and $1^{st}$ mixing duct inlet) effect on ejector pumping performance.