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윤현기(Hyungi Yoon),유일수(Ilsu Yoo),박준영(Junyeong Park),박무룡(Mooryong Park) 한국유체기계학회 2008 유체기계 연구개발 발표회 논문집 Vol.2008 No.-
Multi-stage centrifugal pump is widely used over a variety of industrial field such as power and chemistry plant because of its space efficiency and high exit pressure. The 1<SUP>st</SUP> stage pump performance of the multi -stage centrifugal pump is especially important because it is generally composed of the several pumps which are the same geometry along the same shaft. And return channel is used as a connecting passage between the each pump. In the present study, to find out the loss distribution, hydraulic performance and cavitation characteristic, the 1<SUP>st</SUP> stage pump composed of impeller, diffuser and return channel has been investigated numerically by using the k-ω based SST turbulent model, homogeneous flow model and Rayleigh Plesset cavitation model. The power efficiency, total head raise and HPSHR is 0.88, 129m and 2.84m at the designed point, respectively. The numerical analysis of the cavitation characteristic was studied in case of three different calculation models and it was confirmed that only impeller part is needed to find out the cavitation feature in the 1<SUP>st</SUP> stage pump which includes the return channel.
윤현기(Hyun Gi Yoon),David E. Stock,유기수(Ki Soo Yoo),정명균(Myung Kyoon Chung) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
Diurnal variation of the flow over a forest canopy on a mountain slope is simulated numerically. In the daytime, the earth surface is heated by the solar radiation and the flow goes up the mountain due to the buoyancy force, and during the night, the air is drained downward along the slope owing to the cooling of the surface by radiation. In this flow process the forest canopy that consists of leaf region and the trunk region plays a dominant role as a momentum sink to the flow, thus the modeling of the leaf area region and trunk region is critical to the successful flow simulation. In the present study, a field measurement in an experimental forest in the State of Oregon in the United States is numerically analyzed. The resistance to the flow in the leaf region is directly related to the leaf area density (LAD), and the trunk is modeled as a cylinder.
윤현기(Hyungi Yoon),최범석(Bumseog Choi),정명균(Myungkyoon Chung) 한국유체기계학회 2008 유체기계 연구개발 발표회 논문집 Vol.2008 No.-
A metal diaphragm compressor has been widely used for supplying a high pressure gas. A non-return discharge and suction valve are components of the compressor that draw off the hydrogen gas. Those components are self-actuated by differential pressures. Therefore, the rapid response and the less static pressure loss are required. And the gas sucked in the gas space is compressed by an oscillating diaphragm existed between the hydrogen and oil space. In the present study, to find out the dynamic behavior of the suction, discharge valve and metal diaphragm, the unsteady flow field has been investigated numerically by using the FSI (Fluid Structure Interaction). k-ω turbulent model and mesh deformation. Numerical studies of the check valve and diaphragm are conducted with the pressure change and the displacement of the cylinder with time. respectively.
윤현기(Hyungi Yoon),박무룡(Mooryong Park),유일수(Ilsu Yoo),황순찬(Soonchan Hwang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
The operating cost is highly affected by a small difference of pump efficiency around 1~2% in a high capacity pump. So, the detailed revision of the design is required. In the present study, the pump performance has been investigated experimentally and numerically with a change of a stagger angle. The axis of rotation of the stagger angle is placed at the center of the sectional area of the blade between the hub and shroud. The stagger angle is set as -2, -1, 1 and 2 degree from the original design. Performance analysis of each stagger angle is achieved with various flow rates. Cavitation characteristic is also studied at this time. The impeller and diffuser have been investigated numerically by using the commercial code CFX, k-w based SST turbulent model, homogeneous flow model and Rayleigh Plesset cavitation model. It shows good performance that the stagger angle is one degree. Its performance is very similar with the original design near the design point, but better than 2~3% at the high flow rate. The result of the cavitation characteristicshows that the net positive section head (NPSH) is lower than 10% compared with the original design.
윤현기(Hyun-Gi Yoon),최원철(Won-Chul Choi),유일수(Il-Soo Yoo) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
Blade parts of the Submersible cargo pump consist of inducer, impeller and diffuser. Suction performance of the inducer is important to ensure the safety operation at low NPSHA. A set of 2-bladed inducers are designed in considerations of the cavitation, head raise and outlet flow angle. At here, total head raise through the inducer is determined based on the NPSHR of the impeller. Diffuser of the submersible cargo pump has a geometrical limit due to its operation conditions. In this study, diffuser is designed based on the performance and geometric characteristics of the existed impeller and outline conditions of the cargo pump. And then, on Suction and hydraulic performance of the one set of the cargo pump are simulated numerically to check its design requirement.
제3국 출생 탈북청소년의 힐링캠프 경험을 통한 심리변화 연구(정체성 교육중심)
윤현기 ( Yoon Hyun Kee ) 기독교통일학회 2020 기독교와 통일 Vol.11 No.2
본 연구는 제3국 출생 탈북 청소년의 힐링캠프 경험을 통하여 그들이 겪는 정체성혼란에서 탈출하여 미래 희망적 비전에 도전할 수 있도록 진행되었다. 제3국 출생 탈북 청소년 16명의 힐링캠프 결과 자료수집에서 사례별 접근을 시도하였다. 제3국 출생 탈북청소년 힐링캠프 경험은 정체성혼란의 탈출을 위한 환경적 한계, 언어의 어려움 해소를 위한 대응안, 따라가기 어려운 학교 공부 등, 제한적 문제점 등의 범주로 구성하였다. 제3국 출생 탈북청소년은 한국사회 입국후 한국어 구사능력의 어려움으로 한계를 가지며 수업의 이해부족으로 이어진다. 수업의 흥미 유발은 추락하고 학교와 부모의 생활지도에 어려움을 가중시킨다. 힐링캠프 경험으로 새로운 비전과 미래의 꿈에 도전 할 수 있다. 캠프경험으로 제3국 출생 탈북 청소년의 심리변화를 들여다보며 이중 언어의 자신감을 확장하고 미래를 꿈꿀 수 있는 정책적 방안을 제시하였다. This study has been conducted so that young North Korean refugees born in third countries can be free from their identity confusion and challenge for their future vision of hope through healing camp experiences. A case-by-case approach has been adopted in collecting data on the healing-camping outcome of 16 young North Korean refugees born in third countries. Their healing camp experiences have been classified into environmental limitations on escape from identity confusion, countermeasures for resolving linguistic difficulties, limited problems such as schoolwork difficult to catch up, and so on. In South Korean society, young North Korean refugees born in third countries face limitations due to their lack of Korean proficiency, which leads to a lack of class understanding. They lose Interest in class, adding difficulties to daily living guidance from schools and parents. Healing camp experiences enable them to have a new vision and challenge for a new dream. This study proposes policy measures to look into the young refugees psychological changes through camp experiences, boost their bilingual confidence and help them dream of a better future.
윤현기(Hyungi Yoon),최범석(Beomsuok Choi),박준영(Junyeong Park),안국영(Gukyeong Ahn) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
A metal diaphragm compressor has been widely used for supplying a high pressure hydrogen gas to a hydrogen gas station. A non-return discharge valve is an one component of the compressor that draws off the compressed hydrogen gas. Thos component is self-actuated by differential pressures. Therefore, the rapid response and the less static pressure loss are required. In the present study, to find out the behavior of a valve plunger and static pressure change along the valve, the unsteady flow field has been investigated numerically by using the commercial code CFX. k-w turbulent model, FSI(Fluid Structure Interaction) and mesh deformation are used. Numerical study is conducted for the various pressure differences(△p=0.2, 0.5, 1 and 2bar) between the inlet and outlet of the valve. Significant static pressure drop is observed at the front of the valve plunger because the form of the space between the valve plunger and seat is similar to a convergence nozzle.