• 풍력에너지저널
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• 제14권4호
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• pp.68-74
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• 2023

Research is being actively conducted to increase energy production by increasing the length of wind turbine blades. However, it is difficult to manufacture and transport large-scale blades. Various studies are being conducted on the concept of separate wind turbine blades considering transportation methods and maintenance. In this study, various methods of dividing blades and assembling the divided blades were reviewed. The position of the division when the blades are divided was analyzed.

• Wind and Structures
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• 제32권3호
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• pp.267-281
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• 2021

Bending-twisting coupling induced in big composite wind turbine blades is one of the passive control mechanisms which is exploited to mitigate loads incurred due to deformation of the blades. In the present study, flutter characteristics of bend-twist coupled blades, designed for load alleviation in wind turbine systems, are investigated by time-domain analysis. For this purpose, a baseline full GFRP blade, a bend-twist coupled full GFRP blade, and a hybrid GFRP and CFRP bend-twist coupled blade is designed for load reduction purpose for a 5 MW wind turbine model that is set up in the wind turbine multi-body dynamic code PHATAS. For the study of flutter characteristics of the blades, an over-speed analysis of the wind turbine system is performed without using any blade control and applying slowly increasing wind velocity. A detailed procedure of obtaining the flutter wind and rotational speeds from the time responses of the rotational speed of the rotor, flapwise and torsional deformation of the blade tip, and angle of attack and lift coefficient of the tip section of the blade is explained. Results show that flutter wind and rotational speeds of bend-twist coupled blades are lower than the flutter wind and rotational speeds of the baseline blade mainly due to the kinematic coupling between the bending and torsional deformation in bend-twist coupled blades.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.345-346
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• 2006

This study proposes a development of blades for the 6W class small wind turbine system, which is applicable to relatively low speed region like Korea, and very easy to pitch control. The materials of the blades was used for the still. Electrical properties of blades improved by increasing with wind speed. The maximum output showed at $10^{\circ}$ of pitch angle and about 3.8[W] at 5.5[m/s] of wind speed.

• 조명전기설비학회논문지
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• 제27권11호
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• pp.76-81
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• 2013

In this paper, a corona motor with blade type electrodes has been employed as a wind blower. The rotation speed was influenced significantly by the polarity of applied voltage and the number of blades. Therefore the effect of polarity of applied voltage and the number of blades on the electrical and mechanical fundamental properties of corona motor were investigated experimentally. The rotation speed decreased for increasing of number of blades, because the mass of blades increased. But the amount of air blow increased despite decreasing of the rotation speed, because air volume is not only influenced by rotation speed but also the number of blades and ionic wind which generated between blade tips and a induction electrode. Although space occupied by blades of the corona motor is smaller than the whole area of the blast pipe, wind rises a whole range of a wind blower for such reasons.

• Wind and Structures
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• 제30권2호
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• pp.211-217
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• 2020

Vibrations of a wind turbine blade have a negative impact on its performance and result in failure of the blade, therefore an approach to effectively control vibration in turbine blades are sought by wind industry. The small domestic horizontal axis wind turbine blades induce flap wise (out-of-plane) vibration, due to varying wind speeds. These flap wise vibrations are transferred to the structure, which even causes catastrophic failure of the system. Shape memory alloys which possess physical property of variable stiffness across different phases are embedded into the composite blades for active vibration control. Previously Shape memory alloys have been used as actuators to change their angles and orientations in fighter jet blades but not used for active vibration control for wind turbine blades. In this work a GFRP blade embedded with Shape Memory Alloy (SMA) and tested for its vibrational and material damping characteristics, under martensitic and austenite conditions. The embedment portrays 47% reduction in displacement of blade, with respect to the conventional blade. An analytical model for the actuated smart blade is also proposed, which validates the harmonic response of the smart blade.

• Wind and Structures
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• 제7권5호
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• pp.305-316
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• 2004

In this study, a wind tunnel, that has been developed for experiments of wind turbine rotor blades, has been considered. The deviations of the measurements have been examined after this wind tunnel had been introduced and the measurements on it had been explained. Two different wind turbine rotor blades miniatures have been used for getting better results from the experiments. The accuracy of measurements have been experimented three times repetitively and examined statistically. As a result, wind speed values which this type of wind tunnel and wind turbine rotors need for starting, wind speed in the tunnel, temperature and moisture values, the number of rotor's revolution, and the voltage that is produced in 102 ${\Omega}$ resistance and current values have been determined to be fixed by measurements used. This type of wind tunnel and wind turbine rotor' performance difference and the difference of revolution figures have been determined to be fixed by measurements used.

• Structural Engineering and Mechanics
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• 제63권6호
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• pp.703-712
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• 2017

The composite blades of offshore wind turbines accumulate structural damage such as fatigue cracking due to harsh operation environments during their service time, leading to premature structural failures. This paper investigates various fatigue crack models for reproducing crack development in composite blades and proposes a stochastic approach to predict fatigue crack evolution and to analyse failure probability for the composite blades. Three typical fatigue models for the propagation of fatigue cracks, i.e., Miner model, Paris model and Reifsnider model, are discussed to reproduce the fatigue crack evolution in composite blades subjected to cyclical loadings. The lifetime probability of fatigue failure of the composite blades is estimated by stochastic deterioration modelling such as gamma process. Based on time-dependent reliability analysis and lifecycle cost analysis, an optimised maintenance policy is determined to make the optimal decision for the composite blades during the service time. A numerical example is employed to investigate the effectiveness of predicting fatigue crack growth, estimating the probability of fatigue failure and evaluating an optimal maintenance policy. The results from the numerical study show that the stochastic gamma process together with the proper fatigue models can provide a useful tool for remaining useful life predictions and optimum maintenance strategies of the composite blades of offshore wind turbines.

• 풍력에너지저널
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• 제14권3호
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• pp.100-108
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• 2023

The aim of this study is to develop guidelines for predicting interference between drones and wakes during non-destructive blade inspections in wind power systems. The wake generated by wind towers and blades can affect the stability of drone flights, necessitating the establishment of guidelines to ensure safe and efficient inspections. In order to predict the interference between drones and blades, environmental variables must be considered, including quantification of turbulence intensity in the wake generated by the tower and blades, as well as determining the appropriate distance between the drone and the tower/blades for flight stability. To achieve this, computational fluid dynamics (CFD) analysis was performed using cross-sectional geometries corresponding to the main wind turbine blade and tower span locations. Based on the CFD analysis results, a safe flight path for drones is proposed, which minimizes the risk of collision and interference with towers and blades during maintenance operations of wind power systems. Implementation of the proposed guidelines is expected to enhance the safety and efficiency of maintenance work.

• Wind and Structures
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• 제17권6호
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• pp.589-608
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• 2013

A model is proposed to analyse the along-wind dynamic response of upwind turbines with horizontal axis under service wind conditions. The model takes into account the dynamic coupling effect between rotor blades and supporting tower. The wind speed field is decomposed into a mean component, accounting for the well-known wind shear effect, and a fluctuating component, treated through a spectral approach. Accordingly, the so-called rotationally sampled spectra are introduced for the blades to account for the effect of their rotating motion. Wind forces acting on the rotor blades are calculated according to the blade element momentum model. The tower shadow effect is also included in the present model. Two examples of a large and medium size wind turbines are modelled, and their dynamic response is analysed and compared with the results of a conventional static analysis.

• 한국산학기술학회논문지
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• 제18권11호
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• pp.663-667
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• 2017

최근 화석연료의 사용으로 인한 연료고갈 및 환경문제가 대두되고 있으며 이를 해결하기 위한 대체에너지 개발이 시급한 실정이다. 풍력에너지는 대체에너지 중 지속적으로 무제한 사용할 수 있고 공해물질 배출이 없는 청정에너지로 각광받고 있다. 풍력발전은 바람에너지가 로터 블레이드를 통해서 운동에너지로 변환되고 다시 발전기를 통해서 전기에너지를 발생시키는 에너지 변환기술이며, 풍력발전기의 중요부품인 블레이드의 설계 및 제작은 매우 중요한 요소이지만, 우리나라는 이에 대한 기초자료 및 핵심기술 등이 부족하여 아직도 중요부품들을 외국에서 수입하여 사용하고 있는 실정이다. 본 연구에서는 저 풍속에서도 발전 가능한 다층형 구조의 블레이드를 소형풍력발전기에 적용하여 풍속 및 블레이드 개수에 따른 발전기의 출력특성을 분석하였다. 연구결과, 최대풍속 8m/s일 때 블레이드 3개를 적용하면 블레이드를 1개 및 2개를 적용했을 때보다 발전기 출력전압은 33% 및 18%로 증가되었고, 발전기 출력전류는 33% 및 15%로 증가되었으며 발전기 RPM은 23% 및 13%로 증가되었다. 본 연구에서다층형 구조의 블레이드를 소형풍력발전기에 적용한 결과 발전기의 출력특성이 향상되었고 저 풍속에서도 전기에너지의 수집이 가능함을 확인하였다.