• 한국연소학회지
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• 제6권1호
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• pp.14-19
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• 2001

Interests and importance of down-scale combustor is increasing with the emerging need for miniaturized power source which is now a bottleneck of micro system development. But in down scaled combustor increased heat loss compared to thermal energy generation inhibits the usability and application of the device, so as a preliminary work of down scaled combustor fabrication. Modeling tool for the device should be established, in this study modeling approach of closed vessel combustion phenomena that can express heat loss effect and resulting quenching is proposed and the result is compared with experiment data. From this model heat loss effect following combustor scale down can be further understood, and further more design parameter and analysis tool can be obtained.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1059-1065
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• 2010

본 연구에서는 SMART 원자로의 사류형 원자로냉각재펌프의 축소모형에 대한 수력성능을 예측하기 위하여 설계점을 포함한 다양한 탈설계점에서의 해석을 수행하였다. 계산시간의 효율성을 위하여 임펠러와 디퓨저 각 1개 유로로 이루어진 계산영역을 해석대상으로 선정하였다. 임펠러와 디퓨저간의 정보교환을 위하여 스테이지 기법을 사용하였다. 정상상태 비압축성 유동조건에서 축소모형의 수력성능특성을 파악하기 위하여 해석영역의 입구와 출구에서 압력차를 측정하여 양정, 효율과 축동력을 산출하였다. 수력성능 곡선은 일반적인 사류펌프의 성능특성을 잘 모사하는 것으로 나타났다. 저유량에서의 펌프 내부유동의 복잡한 흐름을 확인 하였다.

• Composites Research
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• 제29권6호
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• pp.369-374
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• 2016

본 연구에서는 굽힘-비틀림 커플링(bend-twist coupled, BTC) 설계개념을 적용한 10 MW급 복합재 풍력 블레이드의 구조 최적 설계를 수행하였다. BTC 설계개념은 동적 하중 상황에서 블레이드의 굽힘과 비틀림 거동 사이의 연동을 유도하여, 단면 받음각 변화에 의한 수동적인 적응 하중저감이 가능하다. 인자연구를 통해 최적의 BTC 설계인자를 추출하여 블레이드 구조설계에 적용하였다. BTC 개념이 동적 하중 감소에 미치는 영향을 가늠하기 위해 블레이드 루트 부에서의 피로등가하중을 계산한 결과, BTC 개념이 적용된 블레이드를 적용한 경우 피로등가하중이 2-3% 정도 감소하는 것을 확인할 수 있었다. BTC 효과를 시험적으로 검증하기 위해 1:29 비율의 블레이드 stiffener 축소모델을 제작하였으며, 정하중 시험을 통해 처짐 거동 시 끝단에서의 비틀림을 측정하였다.

• 전기학회논문지
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• 제66권6호
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• pp.885-891
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• 2017

The energy storage system(ESS) is a core component for exchanging the power system structure of the unidirectional power flow into a bidirectional structure. Its important role has been increasing because it has multiple functions such as output stabilization of new renewable energy, demand management, frequency regulation, etc. However, the performance evaluation technology of ESS in korea is lower than one of advanced countries and the recognition of standardization is also lack compared to advanced countries. Furthermore, in order to more accurately and reliably validate the performance of the ESS in advanced countries, it has been required to perform not only performance testing by H/W devices but also performance verification by S/W tool. Therefore, in order to verify the performance testing of ESS by S/W tool, this paper proposes the modeling method of performance testing devices for MW scaled ESS by using the PSCAD/EMTDC S/W, based on real testing devices in domestic institute. From the simulation results of proposed modeling method, it is confirmed that the proposed modeling method is a useful tool for performance validation of ESS.

• 터널과지하공간
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• 제28권6호
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• pp.692-705
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• 2018

발파를 이용한 터널의 굴착 시 수반되는 가장 큰 문제 중 하나는 발파 시 발생하는 지반진동으로 이를 저감시키기 위한 노력의 일환으로 와이어쏘 장비를 이용하여 터널 심발공 주변에 인공 자유면을 형성하고 이를 통해 파쇄도를 향상시키며 동시에 발파 진동을 저감시키는 기술이 개발되어 오고 있다. 본 연구에서는, 실규모 발파 실험 및 3D-DFPA 해석 기법을 통해 인공 자유면의 구조조건에 따른 진동저감 및 발파 효과에 대한 고찰을 수행하였으며, 이에 더불어 인공 자유면 발파에서의 효율적 설계를 위한 경험적 기준을 제안하였다. 분석 결과, 인공 슬롯 자유면은 홉킨슨 효과에 의한 스폴파괴 유발 및 충격진동의 전파경로 차단 등 발파 진동 저감을 야기하는 것으로 판단되었으며, 인공 자유면이 존재하는 경우, 존재하지 않는 경우에 비해 파쇄체적 및 파쇄효율이 모두 증가하는 경향을 보였다. 이는 인공 자유면이 실제 자유면과 동일한 역할을 수행함에 따라 최소저항선의 감소효과를 야기하는 것으로 판단되었으며, 실험 결과를 토대로 발파 공경 및 최소저항선에 대한 발파 파쇄체적의 상관관계를 도출 및 경험적 설계 기준을 제안하였다. 결론적으로, 인공 자유면 발파를 수행 시 발파 공경 대 최소저항선의 비가 약 5에서 8사이의 값을 갖도록 설계하는 것이 가장 이상적인 표준발파 조건에서의 파쇄효과를 기대할 수 있을 것으로 판단되었다.

• Earthquakes and Structures
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• 제18권2호
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• pp.263-273
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• 2020

The use of energy concepts in seismic analysis and design of structures requires the understanding of the input energy response of multi-degree-of-freedom (MDOF) systems subjected to strong ground motions. For design purposes and non-time consuming analysis, however, it would be beneficial to associate the input energy response of MDOF systems with those of single-degree-of-freedom (SDOF) systems. In this paper, the theoretical formulation of energy input to MDOF systems is developed on the basis that only a particular portion of the total mass distributed among floor levels is effective in the nth-mode response. The input energy response histories of several reinforced concrete frames subjected to a set of eleven horizontal acceleration histories selected from actual recorded events and scaled in time domain are obtained. The contribution of the fundamental mode to the total input energy response of MDOF frames is demonstrated both graphically and numerically. The input energy of the fundamental mode is found to be a good indicator of the total energy input to two-dimensional regular MDOF structures. The numerical results computed by the proposed formulation are verified with relative input energy time histories directly computed from linear time history analysis. Finally, the elastic input energies are compared with those computed from time history analysis of nonlinear MDOF systems.

• 한국태양에너지학회 논문집
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• 제33권3호
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• pp.1-8
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• 2013

In order to identify positive or negative effect of seawall on wind turbine, a wind tunnel experiment has been conducted with a 1/100 scaled-down model of Goonsan wind farm which is located in West coast along seawall. Wind speedup due to the slope of seawall contributed to about 3% increment of area-averaged wind speed on rotor-plane of a wind turbine which is anticipated to augment wind power generation. From the turbulence measurement and flow visualization, it was confirmed that there would be no negative effect due to flow separation because its influence is confined below wind turbine blades' sweeping height.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권3호
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• pp.1098-1112
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• 2018

Achievable sum rate and energy efficiency (EE) are investigated for the massive multiple-input multiple-output (Massive MIMO) downlink with channel aging in the time varying Ricean fading channel. Specifically, the expression of the achievable sum rate of the system for the maximum ratio transmission (MRT) precoder with aged channel state information (CSI) in the time varying Ricean fading channel is first presented. Based on the expression, the effect of both channel aging and the Ricean factor on the power scaling law are studied. It is found that the transmit power of base station (BS) is scaled down by $1/{\sqrt{M}}$(where M is the number of the BS antennas) when the Ricean factor K is equal to zero (i.e., time varying Rayleigh fading channel), indicating that aged CSI does not affect the power scaling law. However, the transmit power of the BS is scaled down by 1/M for the time varying Ricean fading channel (where $K{\neq}0$) indicating that the Ricean factor affects the power scaling law and sum rate, and channel aging only leads to a reduction of the sum rate. Second, the EE of the system is analyzed based on the general power consumption model. Both the theoretical analysis and the simulations show that the channel aging could degrade the sum rate and the EE of the system, and it does not affect the power scaling law.

• 전기학회논문지
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• 제67권8호
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• pp.1024-1030
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• 2018

Recently, the large scaled energy storage system(ESS) which has various functions such as peak saving, demand management, output stabilization of renewable energy and frequency regulation(FR) is being energetically installed and operated. Especially, as the use case of frequency regulation ESS, the KEPCO has demonstrated the total of 376[MW] ESS since 2014. However, there are no operational experiences and international technical standards on frequency regulation application in ESS. Therefore, this paper propose the evaluation algorithm for power system performance of ESS by considering the frequency characteristics between governor of existing generator and frequency regulation ESS, in order to verify the power system performance of ESS. And also, this paper propose an evaluation modeling for small scaled power system including the existing generator, frequency control ESS and customer loads based on the PSCAD/EMTDC S/W. From the simulation results in 360[MW] model power system, it is confirmed that frequency regulation ESS has better performances than conventional generators.

• Earthquakes and Structures
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• 제17권2호
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• pp.163-173
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• 2019

For Special Concentrically Braced Frame (SCBF), it is common that the damage concentrates at a certain story instead of spreading over all stories. Once the damage occurs, the soft-story mechanism is likely to take place and possibly to result in the failure of the whole system with more damage accumulation. In this study, we use a strongback column which is an additional structural component extending along the height of the building, to redistribute the excessive deformation of SCBF and activate more structural members to dissipate energy and thus avoid damage concentration and improve the seismic performance of SCBF. We tested one-third-scaled, three-story, double-story X SCBF specimens with static cyclic loading procedure. Three specimens, namely S73, S42 and S0, which represent different combinations of stiffness and strength factors ${\alpha}$ and ${\beta}$ for the strongback columns, were designed based on results of numerical simulations. Specimens S73 and S42 were the specimens with the strongback columns, and S0 is the specimen without the strongback column. Test results show that the deformation distribution of Specimen S73 is more uniform and more brace members in three stories perform nonlinearly. Comparing Drift Concentration Factor (DCF), we can observe 29% and 11% improvement in Specimen S73 and S42, respectively. This improvement increases the nonlinear demand of the third-story braces and reduces that of the first-story braces where the demand used to be excessive, and, therefore, postpones the rupture of the first-story braces and enhances the ductility and energy dissipation capacity of the whole SCBF system.