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이상혁(Sanghyeok Lee),김민석(Minseok Kim),이중호(Jungho Lee),이종우(Jongwoo Lee) 대한전기학회 2010 대한전기학회 학술대회 논문집 Vol.2010 No.4
현재 전기철도에서는 고성능 유도전동기를 사용하고 있어서 열차속도제어를 위해 벡터제어를 이용하고 있다. 또한 최신에 인버터와 제어이론의 개발로 인해 다양한 방법으로 유도전동기 제어가 가능하다. 따라서 다양한 방법을 적용하기 위해서는 모터블록과 유도전동기의 모델이 필요하다. 유도전동기의 제어 방법으로는 가변전압운전, 가변주파수 운전을 통하여 유도전동기의 토크와 회전수를 제어한다. 철도차량 추진시스템은 많은 서브시스템을 가지고 있어 전체적인 성능을 해석하기가 매우 복잡하다. 본 논문에서는 유도전동기를 사용하는 철도차량 추진시스템을 대상으로 Matlab/Simulink를 이용한 연계 시뮬레이션 모델을 개발하였고, 연계해석 결과를 바탕으로 전동기 구동 분야의 모의 시스템 설계에 대해 연구하였다. 또한 철도차량 추진시스템의 성능을 해석하기 위해 각각 제어기 및 유도전동기를 라이브러리로써 모델화하였다.
이재윤(Jaeyoon Lee),이상혁(Sanghyeok Lee),김현택(Hyeontaek Kim),박용찬(Yongchan Park),이근진(Geunjin Lee),이창헌(Changheon Lee),최성규(Sunggyu Choi),홍순욱(Soonwook Hong) Korean Society for Precision Engineering 2022 한국정밀공학회지 Vol.39 No.2
In this study, Yttria-stabilized zirconia (YSZ) functional layers were applied with different thin-film fabrication process such as sputtering and atomic layer deposition (ALD) to enhance oxygen reduction reaction (ORR) for solid oxide fuel cells. We confirmed that the YSZ functional layer deposited with sputtering showed relatively low grain boundary density, while the YSZ functional layer deposited with the ALD technique clearly indicated high grain boundary density through scanning electron microscopy (SEM) and X-ray diffractometry (XRD) results. The YSZ functional layer coated with the ALD technique revealed that more ORR kinetics can occur using high grain boundary density than the functional layer deposited with sputtering. The peak power density of the SOFC deposited with ALD YSZ indicates 2-folds enhancement than the pristine SOFC.
Lee, Sanghyeok,Park, Mansoo,Kim, Hyoungchul,Yoon, Kyung Joong,Son, Ji-Won,Lee, Jong-Ho,Kim, Byung-Kook,Choi, Wonjoon,Hong, Jongsup Elsevier 2017 ENERGY Vol.120 No.-
<P><B>Abstract</B></P> <P>Elucidating internal thermal conditions of high-temperature solid oxide fuel cell (SOFC) stacks is essential for obtaining a substantial thermal efficiency and reliability for long-term operations prior to their commercialization. To examine simultaneous heat transfer and its generation and their effect on the local thermodynamic state, a high-fidelity physical model that resolves spatially the three-dimensional structure of planar, anode-supported SOFC stacks is used in this study. Results show that thermal conduction through metallic interconnects plays a key role in transferring the heat produced by joule heating and electrochemical reactions and thus determining the internal thermal conditions. The heat generated from the electrolyte and thin reactive electrode layers is transferred to the interconnect predominantly by gaseous convection and conduction through materials in the anode and cathode, respectively. The interconnect subsequently transports this heat conductively towards gas inlets and/or surrounding repeating units, influencing temperature increments, its profile and hot spot formation. Its effect on the internal thermal conditions was further examined by a parametric study with respect to the thermal property and geometry of the interconnect which determine its thermal resistance. They indeed affect significantly heat generation and its transfer within the cell, through its boundaries, between repeating units and to incoming gases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Internal thermal conditions of solid oxide fuel cell (SOFC) stacks are elucidated. </LI> <LI> Heat transfer in the anode and cathode is attributed to different primary pathways. </LI> <LI> Metallic interconnects play a key role in transferring the heat produced from SOFC. </LI> <LI> Interconnects transport heat towards gas inlets and surrounding repeating units. </LI> <LI> Thermal resistance of interconnects influences substantially thermal conditions. </LI> </UL> </P>
Lee, Sanghyeok,Kim, Hyoungchul,Yoon, Kyung Joong,Son, Ji-Won,Lee, Jong-Ho,Kim, Byung-Kook,Choi, Wonjoon,Hong, Jongsup Elsevier 2016 INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER - Vol.97 No.-
<P><B>Abstract</B></P> <P>The thermo-fluid reacting environment and local thermodynamic state in solid oxide fuel cell (SOFC) stacks were examined by using three-dimensional numerical simulations. Enhancing the performance and durability of the SOFC stacks is essential when a high fuel utilization scheme is implemented to increase the system efficiency and lower system operating costs. In this study, numerical simulations were conducted to elucidate the effect of fuel utilization on heat and mass transfer as the fuel utilization is raised. A high-fidelity three-dimensional physical model was developed incorporating elementary electrochemical reaction kinetics by assuming rate-limiting steps and spatially-resolved conservation equations. The model considers planar anode-supported SOFC stacks and is validated against their electrochemical performance experimentally measured. A parametric study with respect to fuel utilization was conducted by varying a fuel flow rate while maintaining other operating conditions constant. Results show that, when increasing the fuel utilization, a narrow and non-uniform electrochemical reaction zone is observed near the fuel inlet, resulting in substantial depletion of hydrogen in the downstream fuel flow and thus raising the partial pressure of oxygen in the anode. This subsequently lowers the electrochemical potential gradient across the electrolyte and hence induces a large gradient of ionic current density along the cell. Convective flow through porous electrodes also results in pressure gradients in the direction of both cell thickness and length. In addition, the heat balance between conduction through metallic interconnects, convection by gases and the heat generated from charged-species transport and electrochemical reactions determines a temperature gradient along the cell and its maximum location. All of these gradients may induce chemical, mechanical and thermal stresses on SOFC materials and corresponding degradation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A high-fidelity three-dimensional SOFC physical model was developed and validated. </LI> <LI> Thermo-fluid reacting environment was elucidated as fuel utilization is raised. </LI> <LI> Hydrogen depletion induces a gradient of ionic current density in the electrolyte. </LI> <LI> Conductive flow through porous electrodes results in large pressure gradients. </LI> <LI> The temperature profile, its increments and maximum location were estimated. </LI> </UL> </P>
Lee, Hyo-Sang,Lee, Joong Suk,Cho, Sanghyeok,Kim, Hyunjung,Kwak, Kyung-Won,Yoon, Youngwoon,Son, Seon Kyoung,Kim, Honggon,Ko, Min Jae,Lee, Doh-Kwon,Kim, Jin Young,Park, Sungnam,Choi, Dong Hoon,Oh, Se Yo American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.50
<P>We report high-performance of ambipolar organic field-effect transistors (FETs) based on the low band gap copolymers of pDPPT2NAP-HD and pDPPT2NAP-OD. The polymers are composed of electron-rich 2,6-di(thienyl)naphthalene (T2NAP) and electron-deficient diketopyrrolopyrrole (DPP) units with branched alkyl chains of 2-hexyldecyl (HD) or 2-octyldodecyl (OD). The polymers were polymerized via Suzuki coupling, yielding optical band gaps of ∼1.4 eV. In the transistor performance test, we observed good ambipolar transport behavior in both polymer films, and pDPPT2NAP-OD displayed hole and electron mobilities 1 order of magnitude higher than the corresponding properties of pDPPT2NAP-HD. Thermal annealing of the polymer films increased the carrier mobilities. Annealing at 150 °C provided optimal conditions yielding saturated film crystallinity and maximized carrier mobility. The highest hole and electron mobilities achieved in these polymers were 1.3 and 0.1 cm<SUP>2</SUP>/(V s), respectively, obtained from pDPPT2NAP-OD. The polymer structure and thermal annealing affected the carrier mobility, and this effect was investigated by fully characterizing the polymer films by grazing incidence X-ray diffraction (GIXD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) experiments. The GIXD data revealed that both polymers formed highly crystalline films with edge-on orientation. pDPPT2NAP-OD, which included longer alkyl chains, showed a higher tendency to form long-range order among the polymer chains. Thermal annealing up to 150 °C improved the polymer film crystallinity and promoted the formation of longer-range lamellar structures. AFM and TEM images of the films were consistent with the GI-XD data. Theoretical calculations of the polymer structures provided a rationale for the relationship between the torsional angle between aromatic rings and the carrier mobility. From the intensive electrical measurements and full characterizations, we find that the chemical structure of polymer backbone and side alkyl chain has a profound effect on film crystallinity, morphology, and transistor properties.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-50/jp309213h/production/images/medium/jp-2012-09213h_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp309213h'>ACS Electronic Supporting Info</A></P>
Lee, Seunghwan,Lee, Sanghyeok,Kim, Hyo-Jin,Choi, Sung Min,An, Hyegsoon,Park, Mi Young,Shin, Jisu,Park, Jung Hoon,Ahn, Junsung,Kim, Donghwan,Ji, Ho-Il,Kim, Hyoungchul,Son, Ji-Won,Lee, Jong-Ho,Kim, Byun The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.31
<P>Solid oxide fuel cell (SOFC) technology offers tremendous potential for highly efficient and clean power generation. However, its commercialization has lagged owing to the lack of long-term stability. Among the various sources of performance degradation, the interdiffusion between the cathode and electrolyte has been identified as a predominant factor. Herein, we demonstrate a highly reliable diffusion-blocking layer that completely suppresses detrimental chemical interactions at elevated temperatures. This diffusion-blocking layer is constructed <I>via</I> a bilayer approach, in which the top and bottom layers perform individual functions to precisely control the bulk and interfacial properties. Harnessing two types of specially designed nanoparticles for each part enables the realization of the desired film structure. Consequently, the formation of insulating phases and decomposition of the cathode are effectively prevented, resulting in a remarkable improvement in performance and stability. The scalability and feasibility of mass production are verified <I>via</I> the fabrication of large cells (10 cm × 10 cm) and a multi-cell stack. The stack in which the bilayer technique is implemented exhibits an extremely low degradation rate of 0.23% kh<SUP>−1</SUP>, which fulfills the strict lifetime requirement for market penetration. This work highlights a scalable, cost-effective, and reproducible method for the production of highly durable multilayer energy devices, including SOFCs.</P>