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현승혁(Hyun, Seung Hyuk),황원섭(Hwang, Won Sub),박성준(Park, Sung Jun) 대한토목학회 2021 대한토목학회논문집 Vol.41 No.3
본 논문에서는 하부수평브레이싱 설치에 따른 무도상 철도판형교의 횡방향 및 비틀림거동에 관한 영향을 검토하였다. 우선 하부브레이싱의 부재 배치 형태가 다른 해석모델을 대상으로 하여 열차하중에 의한 횡방향변위를 비교 검토하여 가장 효율적인 하부 브레이싱의 배치에 대하여 검토하였다. 다음으로는 하부브레이싱을 설치한 2주형 철도판형교의 비틀림거동에 대해 검토를 수행하였다. 또한, FEM 해석결과로부터 구한 비틀림상수와 상부와 하부수평브레이싱을 등가두께로 치환하여 폐합단면으로 하는 철도판형교의 비틀림상수를 비교하였고, 교량의 지간길이와 하부브레이싱의 단면적의 영향을 검토하였다. 이와같은 해석결과를 기초로 본 연구에서는 횡좌굴모멘트와 비틀림상수비와의 관계곡선을 제시하였고 비틀림보강이 필요한 철도판형교의 범위를 제안하였다. In this paper, the effect on the lateral and torsional behavior of ballastless railway plate girder bridge by the installation of the lower horizontal bracing has been reviewed. First of all, the most efficient lower bracing arrangement has been reviewed by comparing and examining the lateral displacement due to the train load, targeting analysis models with different arrangement types of lower bracing. Next, the research on torsional behavior of plate girder bridge with lower bracing has been conducted. In addition, the torsion constant from FEM analysis results has been compared with the torsion constant of a railroad plate girder bridge with a closed section by substituting the upper and lower horizontal bracing with equivalent thickness. Based on this comparison, the impact on the bridge span length and the cross section area of the lower bracing has been examined. Through this study, the curve graph related to lateral buckling moment and torsional constant ratio is presented and the range of plate girder bridge requiring torsional reinforcement is proposed.
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수소연료전지의 성능 향상을 위한 다공성 표면에서의 물 제거에 대한 연구
이경민(Kyeong-Min LEE),박찬경(Chan-Kyung Park),손도협(Do-Hyeop Son),강우성(Woo-Seong Kang),박상혁(Sang-Hyuk Park),현승혁(Seung-Hyuk Hyun),김한상(Han-Sang Kim) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as the power sources to replace internal combustion engines. Water is generated in the catalyst layer of PEMFC and excessive water can cause flooding. It is still an important task to remove water properly to prevent flooding. Hence, proper water management in PEMFCs is a core issue for improving performance and longevity. This study presents the experimental approach to understand the water removal behavior on porous gas diffusion layer (GDL) surfaces in the flow channel of PEMFC. To do this, a sample GDL/flow channel model was fabricated to investigate the water transport characteristics in a PEM fuel cell using direct ex-situ water visualization. Using a high-speed camera, the process from growth to detachment of water droplets is photographed for two types of GDL samples (with micro porous layer (MPL) and without MPL). The contact angle hysteresis (CAH) according to droplet aspect ratio (DAR) at water droplet detachment is mainly investigated is compared with the static contact angle (SCA) of the GDL surface. In addition, at detachment, the DAR and CAH according to air Reynolds number are compared with the SCA. These data show that the adhesion of the GDL surface has a dominant effect on water removal on porous surfaces. It is expected that the data from this study can contribute to the basic design of GDL structures with enhanced water removal characteristics.
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