과도 액정 기법을 이용한 와동발생기 하류의 유동장 및 열전달 측정

홍철현,양장식,이기백,Hong, Cheol-Hyun,Yang, Jang-Sik,Lee, Ki-Baik 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.11

The effects of the interaction between flow field and heat transfer caused by the longitudinal vortices are experimentally investigated using a five hole probe and a transient liquid crystal technique. The test facility consists of a wind tunnel with vortex generators protruding from a bottom surface and a mesh heater. In order to control the strength of the longitudinal vortices, the angle of attack of vortex generators used in the present experiment is 20$^{\circ}$, and the spacing between the vortex generators is 25mm. The height and cord length of the vortex generator is 20mm and 50mm, respectively. Three-component mean velocity measurements are made using a f-hole probe system, and the surface temperature distribution is measured by the hue capturing method using a transient liquid crystal technique. The transient liquid crystal technique in measuring heat transfer has become one of the most effective ways in determining the full surface distributions of heat transfer coefficients. The key point of this technique is to convert the inlet flow temperature into an exponential temperature profile using the mesh heater set up in the wind tunnel. The conclusions obtained in the present experiment are as follows: The two maximum heat transfer values exist over the whole domain, and as the longitudinal vortices move to the farther downstream region, these peak values show the decreasing trends. These trends are also observed in the experimental results of other researchers to have used the uniform heat flux method.

저압 SCR을 위한 디젤발전기 배기가스 온도 변화

홍철현,이창민,이상득 해양환경안전학회 2021 해양환경안전학회지 Vol.27 No.2

To facilitate low-pressure selective catalyst reduction (L.P SCR), a high exhaust-gas temperature of a four-stroke diesel engine for a ship’s generator is required. This study aimed at reducing the exhaust-gas temperature by adjusting the valve open-close timing and fuel injection timing to satisfy the operating conditions of L.P SCR and prevent accidents associated with the generator engine due to high temperature. To lower exhaust-gas temperature, the angle of the camshaft was adjusted and the shim of the fuel injection pump was added. As a result, the maximum explosion pressure increased and the average of the turbocharger outlet temperature dropped. Considering the heat loss from the turbocharger outlet to the SCR inlet, the operation condition for L.P SCR was satisfied with 290 °C. The study demonstrates that safe operation of a diesel generator can be achieved by lowering the exhaust-gas temperature. L.P SCR의 촉매 반응을 위해 선박의 발전기용 4행정 디젤엔진의 배기가스 온도를 높게 설계 할 수밖에 없었다. 본 연구의 목적은 밸브개폐시기와 연료분사시기를 조정을 통한 배기가스의 온도 감소가 L.P SCR의 운전조건을 만족시키고 고온으로 인한 발전기 엔진의 사고를 예방하기 위함이었다. 배기가스 온도를 하강시키기 위해 캠샤프트의 각도를 조정하고 연료분사펌프의 Shim을 추가하였다. 그 결과 최대폭발압력은 12.8bar 증가하였고 터보차저 출구온도 평균값은 13.3℃ 하강하였다. 터보차저 출구에서 SCR 입구까지의 열손실을 감안하더라도 L.P SCR 운전조건인 SCR 챔버 입구 온도인 290℃를 만족하였다. 배기가스 온도 하강을 통해 디젤발전기의 안전운전이 가능하게 한 연구였다.

과도 액정 기법을 이용한 열전달 계수 측정법에 관한 실험적 연구

홍철현,정준화,양장식,이기백 한국마린엔지니어링학회 2003 한국마린엔지니어링학회지 Vol.27 No.5

Heat transfer characteristics of a pair of longitudinal vortices using a transient liquid crystal technique are studied experimentally. In order to control the strength of longitudinal vortices, angle of attack of the vortex generators is $20^{\circ}$and the length of space from the centerline the vortex generations is 25mm apart. The heat transfer measurements using a transfer coefficients. The following conclusions are obtained from the present experiment. When any vortex generators are not set up in wind tunnel test, heat transfer rate is low respectively. However, with the vortex generators of rectangular winglet, the heat transfer on the local surface can be enhanced.

과도액정기법을 이용한 열전달 측정 및 수치해석

홍철현,이기백,양장식,Hong Cheol-Hyun,Lee Ki-Baik,Yang Jang-Sik 한국마린엔지니어링학회 2005 한국마린엔지니어링학회지 Vol.29 No.1

A transient liquid crystal technique has become one of the most effective ways in measuring the local heat transfer coefficients on the entire surface. The key Point of this technique is to convert the inlet flow temperature into an exponential temperature profile using a mesh heater. In order to verify the validity of this technique. the heat transfer characteristics on the wall surface by a pair of longitudinal vortices is investigated experimently and numerically. A standard ${\kappa}-{\varepsilon}$ is used for the numerical analysis of turbulent flow field. It is found from experiment and numerical analysis that two peak values exist over the whole domain. as the longitudinal vortices move to the farther downstream. these peak values decrease and the dimensionless averaged Nusselt number with the lapse of time is maintained nearly at constant values. The experiment results obtained from the present experiment in terms of the transient liquid crystal technique are in good agreement with the numerical results. Therefore, the transient liquid crystal technique developed for the measurement of heat transfer coefficient is proved to be a valid method.

와동간의 상호작용이 경계층 및 열전달에 미치는 영향에 관한 연구 ( I ) - Common flow down에 관하여 -

홍철현,양장식,이기백,Hong, Cheul-Hyun,Yang, Jang-Sik,Lee, Ki-Baik 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.2

This paper describes the results of an experimental investigation of the flow characteristics and the heat transfer rate on a surface by interaction of a pair of vortices. The test facility consists of a boundary-layer wind tunnel with a vortex introduced into the flow by half-delta wings(vortex generators) protruding from the surface. In order to control the strength of the two longitudinal vortices, the angles of attack of the vortex generators are varied from 20 degree to 45 degree, but spacings between the vortex generators are fixed to 4 cm. The 3-dimensional mean velocity downstream of the vortex generators is measured by a five-hole pressure probe, and the hue-capturing method using the thermochromatic liquid crystals has been used to provide the local distribution of the heat transfer coefficient. By using the method mentioned above, the following conclusions are obtained from the present experiment. The boundary layer is thinned in the regions where the secondary flow is directed toward the wall and thickened where it is directed away from the wall. The peak augmentation of the local heat transfer coefficient occurs in the downwash region near the point of minimum boundary-layer thickness. Streamwise distributions of averaged Stanton number on the measurement planes show very similar trends for all the cases(${\beta}=20^{circ},\;30^{\circ}\;and\;45^{\circ}$).

과도 액정 기법을 이용한 와동발생기 하류의 유동장 및 열절달 측정

홍철현,양장식,이기백 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.11

지역혁신을 위한 특화교육트랙 교과과정의 개발

홍철현,박원규,임오강,한명철 한국공학교육학회 2007 공학교육연구 Vol.10 No.4

This paper aims to present the ways to maximize educational effects and facilitate a curriculum renovation through the Specified Track Curriculum Development, a joint lecture system among local universities which is implemented by Busan Educational Alliance of Mechanical Engineering (BEAM) as part of New University for Regional Innovation(NURI), a government-sponsored project to facilitate a balanced regional development of Korea. The Specified Track Curriculum is a unified governing body joined by 4 universities of mechanical engineering departments with an emphasis on their specified academic fields(advanced hightech, environmental, marine and foundational machinery sectors), And the universities mutually recognize academic credits. The track (Specified-Track Curriculum) was carried out three times from winter semester in 2005 to the present and 486 students took the track course for two years. As a result, the track laid out a foundation for the first local joint lecture system in korea with the performance-oriented and students-tailored education, meeting needs of the new era and training efficiency. The graduates' employment rose to 8.5%, compared with that of 2005. According to recent survey conducted on companies employing the graduates, the satisfaction with the graduates' performance marked 9.4% improvement. The track also contributed to expanding human networks, facilitating the educational exchange of local universities. 본 논문에서는 지역균형발전의 일환으로 실시된 지방대학 혁신역량 강화사업(New University for Regional Innovation, NURI) 중 부산권 기계부품산업 혁신인력 양성사업단(Busan Educational Alliance of Mechanical Engineering, BEAM)에서 시행중인 지역대학간 공동강의 시스템인 첨단기계부품 특화교육트랙을 통한 교육효과와 교과과정 개선의 질적 향상방안을 제시하였다. 트랙은 사업단 소속 4개 대학의 기계공학부(과)가 공동주관하며, 각 대학의 특화된 교육과정(첨단기계, 환경기계, 해양기계, 기반기계)을 중심으로 상호학점인정을 통한 교과과정으로 편성되었다. 2005년 동계학기부터 현재까지 3차례의 계절학기를 통하여 실시되었으며, 2년간 총 486명의 학생이 각 트랙과목을 수강하였다. 그 결과 새로운 시대적 요구사항과 학습의 효율성을 동시에 수용하는 성과중심 및 수요자중심의 교육내용으로 국내 최초의 전공별 지역공동강의 제도를 정착시켰으며, 트랙 실시 이전인 2005년 대비 8.5%의 졸업생 취업률 향상과 기업체 임․직원을 대상으로 실시된 설문조사에서 전년대비 9.4%의 수요자 만족도 향상의 성과를 거두었다. 또한, 지역대학간의 교류를 통한 인적 네트워크의 확대라는 긍정적인 결과를 얻을 수 있었다.

종방향 와동쌍의 유동특성과 열전달에 미치는 영향에 관한 연구 ( The Flow Characteristics and Heat Transfer Effects of Longitudinal Vortex Pairs )

홍철현,양장식,이기백 대한기계학회 1999 대한기계학회 춘추학술대회 Vol.- No.-

L.P SCR 운전조건 만족을 위한 연료분사타이밍 조정에 따른 배기가스 온도변화에 관한 연구

홍철현,이창민,이상득 해양환경안전학회 2020 해양환경안전학회 학술발표대회 논문집 Vol.2020 No.06

Groove를 활용한 풍력블레이드 성능향상을 위한 수치적 연구

홍철현(Cheol-Hyun Hong),서성호(Seong-Ho Seo) 한국마린엔지니어링학회 2011 한국마린엔지니어링학회지 Vol.35 No.4