• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.273-279
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• 2011

Turbulent flow analysis around a wind turbine blade was performed to evaluate the power performance of offshore wind turbine. Fluent package was utilized to solve the Reynolds-averaged Navier-Stokes equations in non-inertial rotating coordinates. The realizable k-$\varepsilon$ model was used for turbulence closure and the grid system combining structured and unstructured grids was generated. In the first, lift and drag forces of 2-D foil section were calculated and compared with existing experimental data for the validation. Then torque and thrust of the wind turbine blade having NACA 4-series sections were calculated with fixed pitch angle and rpm. Tip speed ratio was varied by changing wind speed. In the next, three kinds of end plate were attached at the tip of blade in order to increase the power of the wind turbine. Among them the end plate attached at the suction side of the blade was found to be most effective. Furthermore, performance analysis with tilt angle and rake was also performed.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.250-251
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• 2010

본 연구는 수평축(horizontal axis) 풍력 터빈에 의해서 수직축 발전기를 운전하는 구조 및 그 운전 방식에 관한 것으로서 바람에 의해 수평축 터빈 로터로 입력된 회전력을 기계적으로 두 개의 수직축 회전 성분으로 변환하여 이들로부터 전기 에너지를 얻어내고 필요에 따라 터빈 날개가 바람이 부는 방향을 향하도록 yaw-axis 제어를 하는 기술에 관한 것이다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.22-22
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• 1997

무공해 에너지원은 화석에너지의 고갈과 환경오염의 심각한 문제로 인하여 절실히 요구되고 있는 실정이다. 그중 풍력발전 시스템은 타 에너지원에 비해 여러 가지 측면에서 유리한 점을 가치고 있다. 본 연구에서는 500Kw급 풍력발전 시스템을 개발함에 있어, 적합한 공력 성능 및 구조성능을 가지는 회전날개 설계과정을 수행하였다. 공력설계는 운용지역의 풍황을 고려하여 회전날개의 외형을 결정하였고 이를 바탕으로 공력성능해석이 수행되었으며, 구조설계는 복합재료를 사용하여 쉘-스파 구조를 갖도록 설계하여 굽힘 및 비틀림 그리고 피로수명에 대한 구조해석이 수행되었다. 그 결과 4m/s의 미풍에서도 운용가능하며, 12m/s에서는 정격출력 550Kw를 생산할 수 있는 형상이 설계되었고, 또한 20년 이상의 피로수명이 확보되었으며, 공질 등의 동적인 문제도 발생하지 않음을 확인하였다.

• The Journal of the Acoustical Society of Korea
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• v.32 no.5
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• pp.369-376
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• 2013

Using Lowson's acoustic analogy, low frequency noise of a wind turbine (WT) is predicted in time domain and the noise sources contributing to the low frequency noise is analyzed. To compute averaged pressure distribution on blades of the WT as noise source, XFOIL is utilized. The blade source domain is divided into several segments along the span direction to compute force exerted on air surrounding the blade segments, which is used as input for noise prediction. The noise sources are decomposed into three terms of force fluctuation, acceleration and velocity terms and are analyzed to investigate each spectral contribution. Finally, predicted spectra are compared with measured low frequency noise spectrum of a wind turbine in operation. It is found that the force fluctuation component contributes strongly in low frequency range with increasing wind speed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.269-274
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• 2014

In this study, low noise designs for a Savonius wind turbine were numerically investigated. As was reported in our previous study, the harmonic components with a fundamental frequency higher than the BPF were identified as being dominant in the noise spectrum of a Savonius wind turbine, and these components were a result of vortex shedding. On a basis of this observation, an S-shaped blade tip is proposed as a means of reducing the noise generated by small vertical(Savonius) wind turbines. This blade induces phase differences in the shedding vortices from the blades, and thus reduces the noise from the wind turbine. The aerodynamic noise characteristics of the conventional and "S-shaped" Savonius turbines were investigated by using the Hybrid CAA method where the flow field around the turbine is computed using the CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow field data. The degree of noise reduction resulting from the proposed design and its reduction mechanism were confirmed by comparing the predicted noise spectrum of these turbines and the flow characteristics around them.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.123-132
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• 2015

In this study, an arrangement design process for multiple wind turbines, placed on the 10MW class floating wave-offshore wind hybrid power generation system, was presented, and the aerodynamic performance was evaluated by using a computational fluid dynamics. An arrangement design, which produces a maximum power in the site wind field, was found by using a commercial program, WindPRO, based on a blade element momentum theory, then the effect of wake interference on the system between multiple wind turbines was studied and evaluated by using ANSYS CFX.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.487-495
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• 2012

The yaw control, a major part of the wind turbine, is closely related to the efficiency of electric power production and the mechanical load. The yaw error, which results from the nacelle not being appropriately aligned in the wind direction, not only decreases the power output but also reduces the lifetime of the wind turbine as a result of large fatigue loads. However, the yawing rate cannot be increased indefinitely because of constraints on mechanical loads. This paper investigates the characteristics of an active yaw control system, the basic principle of the system, and mechanical loads around the yaw axis during yawing.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.7
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• pp.841-847
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• 2018

Since global energy consumption and demand for energy have dramatically risen, a focus on environmental problems and sustainability has become more important. Clean and renewable energy sources such as offshore wind power generation have received attention among new renewable energy options as alternative energy resources. Due to maintenance and operational perspectives, offshore wind farms have been planned for installation in many coastal waters. However, development of offshore wind farms faces interference from existing maritime traffic along the planned areas. In order to safely and effectively govern marine traffic in the vicinity of wind farms and inner areas, standard criteria are suggested to allow vessels to sail the internal waters of offshore wind farm areas. Therefore, the purpose of this study is to establish allowable criteria for sailing vessels and safety zones for offshore wind farms by investigating the local regulations of various offshore wind farm cases overseas. The commended inner safety zone of wind farms is proposed to be a distance of 150 % of the rotation diameter of the wind turbine rotor and a distance of 200 m from the outer wind turbine for the outer safety zone. Besides this, the allowable criteria for sailing vessels within a wind farm is proposed to have an air draft of 14.47 m south-west wind farm sea areas for a minimum margin to avoid hull contact through evaluation of the tide and height of a wind turbine. further studies will be needed to establish vessel sailing criteria among adjacent offshore wind farms as well as vessel sailing criteria within a single offshore wind farm.

• The KSFM Journal of Fluid Machinery
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• v.14 no.2
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• pp.5-10
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• 2011

The purpose of this study is to develop a software for the performance evaluation and blade design of a pitch-controlled HAWT using BEMT(Blade Element Momentum Theory) with Prandtl's tip loss. The HERACLES V2.0 software consist of three major part ; basic blade design, aerodynamic coefficient mapping and performance calculation including stall or pitch control option. A 1MW wind turbine blade was designed at the rated wind speed(12m/s) composing five different airfoils such as FFA-W-301, DU91-W250, DU93-W-210, NACA 63418 and NACA 63415 from hub to tip. The mechanical power predicted by BEMT at the rated wind speed is about 1.27MW. Also, CFD analysis was performed to confirm the validity of the BEMT results. The comparison results show good agreement about the error of 6.5% in rated mechanical power.

• Journal of computational fluids engineering
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• v.18 no.1
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• pp.91-97
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• 2013

In the present study, the effects of contaminant accumulation and surface roughness on the aerodynamic performance of wind turbine blade sections were numerically investigated by using a flow solver based on unstructured meshes. The turbulent flow over the rough surface was modeled by a modified ${\kappa}-{\omega}$ SST turbulence model. The calculations were made for the NREL S809 airfoil with varying contaminant sizes and positions at several angles of attack. It was found that as the contaminant size increases, the degradation of the airfoil performance becomes more significant, and this trend is further amplified near the stall condition. When the contaminant is located at the upper surface near the leading edge, the loss in the aerodynamic performance of the blade section becomes more critical. It was also found that the surface roughness leads to a significant reduction of lift, in addition to increased drag.