• Smart Structures and Systems
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• 제24권3호
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• pp.379-390
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• 2019

In this research, we propose an energy harvesting structure with a flexible blade element vibrating at its first mode to maximize the power output of the piezoelectric material. For this purpose, a piezoelectric patch was attached on the blade element used in a small-scale wind turbine, and air load was applied with a suitable angle of attack in the stall zone. The aerodynamic load created by air excitation vibrates the blade element in its first natural frequency and maximizes the voltage output of the piezoelectric patch. The variation of power outputs with respect to electrical resistance, air speed, and extra mass is experimentally investigated for various cases. An analytical model is constituted using a single-mode blade element with piezoelectric patch dynamics, and the power outputs of the obtained model are compared with experimental results.

• 한국콘텐츠학회논문지
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• 제19권11호
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• pp.365-374
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• 2019

항공운항사고율은 항공기 비정상 자세(Upset)로 인한 조종능력상실(LOC-­I: Loss of Control in Flight)이 가장 높아 ICAO(International Civil Aviation Organization: 국제민간항공기구)는 TEM(Threat and Error Management)을 활용하여 비정상자세 예방 및 회복훈련(UPRT: Upset Prevention & Recovery Training)을 하도록 권고하였다. 그러나 전 세계적으로 항공기 비정상 자세에 관한 TEM 요인 연구가 많이 도출되지 않은 관계로 항공사들이 실질적인 TEM 훈련에 참고할 자료가 많지 않은 실정이다. 본 연구의 목적은 UPRT의 소개와 항공기 비정상 자세로 인한 대표적 사고 3건을 ICAO에서 권고하는 TEM으로 분류하여 핵심요소인 위협과 에러, 불안전항공기 상태의 공통요인을 도출하여 살펴보는 것이다. 본 논문에서 대표적인 비정상자세 사고를 TEM을 활용하여 분류한 결과 공통위협으로는 야간비행/IFR, 자동화 놀람, 부적절한 훈련과 미숙련 부기장 편조로 나타났다. 공통 에러로는 부적절한 엔진 추력, 절차적용오류, 조종, 속도이탈 및 고도 이탈, 의사소통실패, 항공기 이상자세, 복창실패, 크로스 체크 실패 등으로 나타났으며, 불안전항공기 상태로는 부적절한 자동화 모드, 저속이탈, 수직 이탈, 부정확한 엔진 추력 등으로 실속하여 추락한 것으로 나타났다. 또한 공통요인으로부터 개선방향을 도출하여 본 연구는 시작단계에 있는 TEM활용 Upset 향상 방안을 제시하고자 한다.

• 한국유체기계학회 논문집
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• 제18권6호
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• pp.63-70
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• 2015

This paper proposes a novel airfoil named "KA2" for the blade of the wind turbine systems. Dynamic loads characteristics are analyzed and compared using aerodynamic data of ten airfoils including the proposed airfoil. The blade is divided into the sixteen elements in the longitudinal direction of the blade for applying the Blade Element Method Theory (BEMT) method, and in each element, torque, thrust, and pitching moment are calculated using turbulent time varying wind speed and aerodynamic data of each wing. Additionally, each force and torque is accumulated in the whole region of the blade for the estimation of representative values. The magnitude of such forces is comparatively analyzed for different airfoils. The angle of attack is constant below the rated wind speed due to the fact that the tip speed ratio is kept at the constant value, and it increases in the region of over rated wind speed as the tip speed ratio decreasing with constant rated rpm and increasing wind speed. Such increase in the angle of attack causes the changes of the force acting on the airfoil with different characteristics of lift and drag in the stall region of each different airfoil. Even though the mean wind speed is in the rated speed in a given time, because of the turbulence, it has either the over rated or under rated speed most of the time. Furthermore, the dynamic properties of each force are analyzed in this rated wind speed in order to objectively understand the dynamic properties of the blades which are designed based on the different airfoils. These dynamic properties are also compared by the standard deviation of time varying characteristics. Moreover, the output characteristics of the wind turbine are investigated with different airfoils and wind speeds. Based on these investigations, it was revealed that the proposed airfoil (KA2) is well applicable to the blade with passive pitch control system.

• 대한기계학회논문집B
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• 제32권7호
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• pp.549-557
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• 2008

Despite of the laminar-turbulent transition region co-exist with fully turbulence region around the leading edge of an airfoil, still lots of researchers apply to fully turbulence models to predict aerodynamic characteristics. It is well known that fully turbulent model such as standard k-model couldn't predict the complex stall and the separation behavior on an airfoil accurately, it usually leads to over prediction of the aerodynamic characteristics such as lift and drag forces. So, we apply correlation based transition model to predict aerodynamic performance of the NREL (National Renewable Energy Laboratory) Phase IV wind turbine. And also, compare the computed results from transition model with experimental measurement and fully turbulence results. Results are presented for a range of wind speed, for a NREL Phase IV wind turbine rotor. Low speed shaft torque, power, root bending moment, aerodynamic coefficients of 2D airfoil and several flow field figures results included in this study. As a result, the low speed shaft torque predicted by transitional turbulence model is very good agree with the experimental measurement in whole operating conditions but fully turbulent model(${\kappa}-\;{\varepsilon}$) over predict the shaft torque after 7m/s. Root bending moment is also good agreement between the prediction and experiments for most of the operating conditions, especially with the transition model.

• 한국항행학회논문지
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• 제10권4호
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• pp.319-326
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• 2006

본 논문에서는 연료 유량만을 제어 입력으로 하는 터보제트 엔진 제어기를 제안한다. 퍼지 기반 제어기는 무인 항공기의 가감속시 서지와 flame-out 현상이 발생되지 않도록 효율적으로 제어 입력을 생성하며, 항공기 기동시 빠른 가감속 특성을 보이며, 동작점이 서지라인과 flame-out라인 사이에 존재하도록 설계되었다. 엔진 회전 속도와 서지 여유가 퍼지 입력 변수가 되고, 신속하고 안전하게 항공기가 원하는 회전속도로 수렴할 수 있도록 제어기를 설계한다. 제안된 제어기의 성능확인을 위해 MATLAB을 사용한 컴퓨터 시뮬레이션을 수행하였으며, DYGABCD 프로그램을 사용하여 생성된 선형 엔진 모델에 적용하여 성능을 입증하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.396-401
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• 2002

The purpose of this 3-D numerical simulation is evaluate the application of a commercial CFD code to predict 3-D flow characteristics of wind turbine. The experimental approach, which has been main method of investigation, appears to be its limits, the cost increasing disproportionally with the size of the wind turbines, and is hence mostly limited to observing the phenomena. Hence, the use of Computational Fluid Dynamics (CFD) techniques and Wavier-Stokes solvers are considered a very serious contender. The flow solver CFX-TASCflow is employed in all computations presented in this paper. The 3-D flow separation and the wake distribution of 2 bladed Horizontal Axis Wind Turbines (HAWTs) are compared to Heuristic model and visualized result by NREL(National Renewable Energy Laboratory). Simulated 3-D flow separation structure on the rotor blade is very similar to Heuristic model and the wake structure of the wind turbine is good agree with visualized results.

• 한국항공우주학회지
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• 제36권10호
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• pp.1017-1025
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• 2008

본 연구에서는 무인항공기의 대기속도 및 압력고도를 측정하는 공력자료시스템(ADS)을 개발하였다. ADS는 비행제어시스템에 항공기 속도와 고도를 제공함으로써 실속속도 이하에서의 비행을 막고 고도유지 비행을 가능하게 하는 시스템이다. 무인항공기의 속도와 고도를 정확하게 측정하는 것은 비행성능을 확인하고 항공기의 안전성을 보장하기 위한 중요한 부분이다. 본 논문에서 개발된 ADS는 MEMS 압력센서, 저역통과필터, 마이크로 컨트롤러 그리고 피토튜브로 구성되어 있다. 온도보정과 압력보정을 통해 ADS 데이터의 오차를 줄였으며 비행시험에서 GPS 데이터와 ADS 데이터를 비교하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2000년도 유체기계 연구개발 발표회 논문집
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• pp.163-168
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• 2000

A method to search the design parameters for optimum stage matching has been used based on a 1-D mathematical model of a compressor, which uses the data obtained from the preliminary test to identify the design parameters. This methodology was applied with a two-stage axial compressor, which was originally designed for a helicopter gas turbine engine. After Identifying design parameters using preliminary test data, an optimization process has been employed to achieve the best matching between the stages (i.e., maximum efficiency of the compressor at its operation modes within a given range of the rotor speed under given restrictions for required stall margins and mass flow). 3-D flow calculations have been performed to confirm the usefulness of the corrections based on 1-D mathematical model. Calculational results agree well with the experimental data in view of the performance characteristics. Some promising results were produced through the methodology proposed in this paper in conjunction with flow calculations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2192-2197
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• 2003

The purpose of this 3-D numerical simulation is evaluate the application of a commercial CFD code to predict 3-D flow and power characteristics of wind turbines. The experimental approach, which has been main method of investigation, appears to be its limits, the cost increasing with the size of the wind turbines, hence mostly limited to observing the phenomena on rotor blades. Therefore, the use of Computational Fluid Dynamics (CFD) techniques and Navier-Stokes solvers are considered a very serious contender. The flow solver CFX-TASCflow is employed in all computations in this paper. The 3-D flow separation and the wake distribution of 2 and 3 bladed Horizontal Axis Wind Turbines (HAWTs) are compared to Heuristic model and smoke-visualized experimental result by NREL(National Renewable Energy Laboratory). Simulated 3-D flow separation structure on the rotor blade is very similar to Heuristic model and the wake structure of the wind turbine is good consistent with smoke-visualized result. The calculated power of the 3 bladed rotor by CFD is compared with BEM results by TV-Delft. The CFD results of which is somewhat consist with BEM results, under an error less than 10%.

• Journal of Advanced Marine Engineering and Technology
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• 제27권7호
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• pp.906-913
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• 2003

The purpose of this 3-D numerical simulation is to evaluate the application of a commercial CFD code to predict 3-D flow and power characteristics of wind turbines. The experimental approach, which has been main method of investigation, appears to be its limits, the cost increasing with the size of the wind turbines, hence mostly limited to observing the phenomena on rotor blades. Therefore. the use of Computational Fluid Dynamics (CFD) techniques and Navier-Stokes solvers are considered a very serious contender. The flow solver CFX-TASCflow is employed in all computations in this paper. The 3-D flow separation and the wake distribution of 2 and 3 bladed Horizontal Axis Wind Turbines (HAWTs) are compared to Heuristic model and smoke-visualized experimental result by NREL(National Renewable Energy Laboratory). Simulated 3-D flow separation structure on the rotor blade is very similar to Heuristic model and the wake structure of the wind turbine is good consistent with smoke-visualized result. The calculated power of the 3 bladed rotor by CFD is compared with BEM results by TU-Delft. The CFD results of which is somewhat consist with BEM results. under an error less than 10%.