• 한국유체기계학회 논문집
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• 제15권2호
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• pp.63-68
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• 2012

This paper deals with the aerodynamic analysis and structural test under estimated loading condition for small composite blade, which is utilized in dual rotor wind turbine system. Firstly, the front and rear blades of dual rotor wind turbine system were modeled using reverse engineering method. And using finite volume method, the aerodynamic forces were analyzed at the rated and cutout wind speed to identify the pressure distribution on blades. And then, the full scale structural tests were conducted according to load and strength based methodology in IEC 61400-2 to identify the structural integrity of composite blade.

• Smart Structures and Systems
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• 제20권3호
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• pp.311-328
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• 2017

The characteristics of boundary layers have significant effects on the aerodynamic forces and vibration of the wind turbine blade. The incorporation of active trailing edge flaps (ATEF) into wind turbine blades has been proven as an effective control approach for alleviation of load and vibration. This paper is aimed at investigating the effects of external trailing edge flaps on the flow pattern and velocity distribution within a boundary layer of a NREL 5MW reference wind turbine, as well as designing a new type of velocity sensors for future validation measurements. An aeroelastic-aerodynamic simulation with FAST-AeroDyn code was conducted on the entire wind turbine structure and the modifications were made on turbine blade sections with ATEF. The results of aeroelastic-aerodynamic simulations were combined with the results of two-dimensional computational fluid dynamic simulations. From these, the velocity profile of the boundary layer as well as the thickness variation with time under the influence of a simplified load case was calculated for four different blade-flap combinations (without flap, with $-5^{\circ}$, $0^{\circ}$, and $+5^{\circ}$ flap). In conjunction with the computational modeling of the characteristics of boundary layers, a bio-inspired hair flow sensor was designed for sensing the boundary flow field surrounding the turbine blades, which ultimately aims to provide real time data to design the control scheme of the flap structure. The sensor element design and performance were analyzed using both theoretical model and finite element method. A prototype sensor element with desired bio-mimicry responses was fabricated and validated, which will be further refined for integration with the turbine blade structures.

• 한국전산구조공학회논문집
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• 제25권3호
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• pp.203-209
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• 2012

본 논문에서는 상온 및 방사선 경화 복합재 풍력 블레이드의 구조성능을 비교하기 위하여 단면 강성, 정적응력 및 동적 고유 진동수를 해석하였다. 먼저 상온 및 방사선 경화공정에 의한 복합재료 시편의 탄성계수 등 물성 값을 적용하였다. 블레이드의 단면 강성 값은 고형 복합재료 보 이론을 적용하여 유한요소 적분법으로 계산하였다. 허브 체결부위를 포함한 소형 풍력 블레이드를 상용 유한요소 프로그램으로 모델링하여 최대 변위와 응력분포 등을 확인하였다. 또한, 풍력 블레이드의 회전속도에 따른 원심력 효과를 고려하여 고유 진동수 해석을 병행하였다. 이와 같은 일련의 해석결과를 상호 비교함으로써, 상온 및 방사선 경화 복합재료의 물성 값 차이에서 기인하는 풍력 블레이드의 구조성능 변화를 정량적으로 분석하였다.

• 한국산학기술학회논문지
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• 제18권12호
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• pp.88-92
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• 2017

풍력은 자원이 풍부하고, 끊임없이 재생되며, 공해물질 배출이 없어서 친환경적인 점에서 화석에너지 고갈 시에 대비한 유망한 대체 에너지원으로서 각광받는 에너지이다. 풍력발전기는 회전축의 방향에 따라 수평축 풍력발전기와 수직축 풍력발전기로 구분되며, 수직축은 발전효율이 낮은 단점이 있는 반면에 바람의 방향에 영향을 받지 않아 요잉 시스템이 필요가 없어 구조가 간단하고, 저 풍속에서도 풍력발전이 가능한 장점이 있어 현재 소형 수직축 풍력발전기가 주목받고 있다. 본 연구에서는 저 풍속에서도 발전 가능한 자이로밀형, 힌지형, 양문형의 블레이드 형태에 따른 소형 수직형 풍력발전기를 이용하여 1m/s~11m/s의 가변풍속에 따른 발전기의 출력전압 및 출력전류를 분석하였다. 연구결과 최대풍속 11m/s일 때 발전기 출력전압은 양문형 블레이드를 적용 시 자이로밀형 블레이드보다 67%, 힌지형 블레이드보다 9%가 증가되었으며, 발전기 출력전류는 양문형 블레이드를 적용 시 자이로밀형 블레이드보다 93%, 힌지형 블레이드보다 5%가 증가되었다. 본 연구를 통해 저풍속 및 고풍속에서의 발전이 용이한 양문형 블레이드의 우수한 출력특성과 실용화 가능성을 확인하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.147-154
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• 2010

The world is gradually running short of fossil fuel. Currently, the role of wind turbine is attracting great attention from all over the world. The objective of this study is to investigate blades of Vertical-axial wind turbine (VAWT) for optimum design using the CFD from the aerodynamics point of view. Because one of the performance of wind turbine depends on shape of blades, the study of comparing one gyro mill type blade and a modified one was carried out. Using the results of computation, we calculated and compared RPM for both models at same wind velocity. And we calculated angular acceleration and moment of inertia to find torque in every time-step. And the pressure contour and velocity profile around the blade were analyzed Also, this study is performed to calculate the wake effect.

• Wind and Structures
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• 제38권5호
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• pp.341-354
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• 2024

This paper presents a theoretical method to deal with the aerodynamic performance and pitch optimization of the horizontal axis wind turbine blades at low wind speeds. By considering a blade element, the functional relationship among the angle of attack, pitch angle, rotational speed of the blade, and wind speed is derived in consideration of a quasi-steady aerodynamic model, and aerodynamic loads on the blade element are then obtained. The torque and torque coefficient of the blade are derived by using integration. A polynomial approximation is applied to functions of the lift and drag coefficients for the symmetric and asymmetric airfoils respectively, where specific expressions of aerodynamic loads as functions of the angle of attack (which is a function of pitch angle) are obtained. The pitch optimization problem is investigated by considering the maximum value problem of the instantaneous torque of a blade as a function of pitch angle. Dynamic pitch laws for HAWT blades with either symmetric or asymmetric airfoils are derived. Influences of parameters including inflow ratio, rotational speed, azimuth, and wind speed on torque coefficient and optimal pith angle are discussed.

• 대한기계학회논문집A
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• 제36권11호
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• pp.1427-1432
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• 2012

풍력터빈이 점차 대형화 되면서 로터 직경도 점차 커지고 있다. 로터 블레이드는 윈드시어와 타워교란 효과로부터 기계적 하중을 받게 된다. 이러한 기계적 하중은 풍력터빈의 수명을 단축시킨다. 따라서, 풍력터빈의 크기가 커짐에 따라 기계적 하중 완화를 위한 풍력터빈 제어 시스템 설계가 중요하다. 본 논문에서는 로터 블레이드의 기계적 하중 저감을 위한 개별 피치 제어에 대해 소개하고 IPC 성능 검증을 위해 시뮬레이션을 통하여 논의한다.

• Wind and Structures
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• 제19권2호
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• pp.199-217
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• 2014

Reported experimental and computational fluid dynamic (CFD) studies have demonstrated significant power augmentation of diffuser shrouded horizontal axis micro wind turbine compared to bare turbine. These studies also found the degree of augmentation is strongly dependent on the shape and geometry of the diffuser such as length and expansion angle. However study flow field over the rotor blades in shrouded turbine has not received much attention. In this paper, CFD simulations of an experimental diffuser shrouded micro wind turbine have been carried out with the aim to understand the mechanisms underpinning the power augmentation phenomenon. The simulations provide insight of the flow field over the blades of bare wind turbine and of shrouded one elucidating the augmentation mechanisms. From the analysis, sub-atmospheric back pressure leading to velocity augmentation at the inlet of diffuser and lowering the static pressure on blade suction sides have been identified as th dominant mechanisms driving the power augmentation. And effective augmentation was achieved for ${\lambda}$ above certain value. For the case turbine it is ${\lambda}$ greater than ${\approx}2$.

• 대한기계학회논문집A
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• 제40권4호
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• pp.407-414
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• 2016

풍력터빈이 MW급으로 대형화되면서 블레이드의 길이가 40미터 이상으로 길어지게 되어, 로터 블레이드가 회전할 때 블레이드에 발생하는 비대칭하중이 증가하게 되었다. 윈드쉬어, 타워 섀도우, 난류풍속 같은 요소들은 블레이드에 이런 비대칭하중 발생에 영향을 미친다. 본 논문은 원드쉬어로 인해 블레이드에 발생하는 추력변동에 의한 동하중을 추력계수를 이용하여 모델링하는 방법에 관한 것이다. 이를 위하여 "윈드쉬어 추력변동 계수"를 정의 및 도입하고, 2MW 육상용 풍력터빈을 대상으로 정격이하의 풍속에서 윈드쉬어 추력변동 계수값을 구하여 분석한다. 구해진 "윈드쉬어 추력변동 계수"와 추력계수를 이용하여 Matlab/Simulink에서 윈드쉬어 동하중 모델을 구현하고, 윈드쉬어에 의해 세 블레이드에 작용하는 추력변동을 추력계수와 "윈드쉬어 추력변동 계수"를 동시에 이용하여 표현할 수 있음을 보인다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권3호
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• pp.236-245
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• 2017

Purpose: There is no established inspection system for composite wind blade during the fabrication stage even though the blades are one of the most important part at wind generation system, but phased array ultrasonic testing method has been continuously studied about wind turbine blade with composite. When wind turbine blade with complex shape by phased array probe is inspected, it is necessary to study for system keeping constant pressure using pressure device. Methods: In this paper, we propose constant pressure device for inspecting wind turbine blade by phased array ultrasonic test method. Design of the device controller is based on Hunt-Crossley model. We evaluate reliability of phased array ultrasonic inspection result that applicated constant pressure device. Result: Defect indication is precise and its error is small when constant pressure mechanism based on Hunt-Crossley model was used. Conclusion: When inspection is progressed using constant pressure mechanism, the reliability of composite wind blade inspection can be improved.