CFD investigation on the flatback airfoil effect of 10 MW wind turbine blade

정재호,김수현 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.5

The flatback airfoil effect on the inboard region of a large wind turbine blade was investigated by numerical analysis. Complicated flow phenomena in wind turbine blade with flatback and non-flatback airfoil were captured by Reynolds-averaged Navier–Stokes flow simulation with shear stress transport turbulence model. Although both airfoil blades were designed using blade element momentum theory to produce identical shaft power, results of three-dimensional computational fluid dynamics (CFD) flow analysis indicated that at a specific location of the root area, the flatback airfoil improved the inboard force by approximately 6 % compared with the non-flatback airfoil. We were also able to confirm that by using the flatback airfoil, the overall shaft power throughout the blade increased by 1 %, thereby restraining the bending moment exerted by the thrust force on the hub by 0.5 %. Moreover, numerical analysis results indicated that the flatback airfoil blade reduced the size of the secondary vortex around the blade root area and its progress in the secondary direction in comparison with the non-flatback airfoil blade. The shape of the flatback airfoil on the trailing edge weakened the adverse pressure gradient migrating from the lower to the upper surface. Regardless of the flatback airfoils, the tip vortex core of the outboard region formed on the suction surface leading edge and strongly rolled up by the pressure surface boundary layers due to the large pressure difference between the suction and pressure surfaces in the blade tip region. This remarkable strong tip vortex developed downstream and raked up the boundary layer of the blade trailing edge with low energy.

Performance Comparison of Two Airfoil Rotor Designs for an Agricultural Unmanned Helicopter

( Young Mo Koo ) 한국농업기계학회 2012 바이오시스템공학 Vol.37 No.1

Purpose: The most important element of an agricultural helicopter is the rotor blade realizing lift force. In order to improve the performance of the rotor blades, two types (KA152313 and KB203611) of airfoils were designed and compared. Methods: The nose shape of the KB203611 airfoil was ``drooped`` and ``sharp`` compared to the leading edge of the KA152313 airfoil. The performance of the experimental airfoils was simulated using CFD-ACE program, and lifts were measured in situ using the ``AgroHeli-4G``, a prototype helicopter. Results: Simulated lifts of the blade with the KA152313 airfoil showed proper values for a wide range of angles of attack between 14°~18°, while the simulated lift of the KB203611 blade exhibited maximum values near 13°~14°. In the lift measurements, the range of operable angles of attack was a collective pitch angle at the grip (GP) of 12°~18° for the KA152313 blade. On the other hand, the range of angles of attack for the KB203611 blade was a GP of 12°~14°. Conclusions: The blade of KA152313 performed well over a wide range of AoAs and the blade of KB203611 performed better at low AoAs. In this study, a variative airfoil blade, gradually emerging from grip to tip using the two different airfoils, was suggested.

Performance Comparison of Two Airfoil Rotor Designs for an Agricultural Unmanned Helicopter

구영모 한국농업기계학회 2012 바이오시스템공학 Vol.37 No.1

Purpose: The most important element of an agricultural helicopter is the rotor blade realizing lift force. In order to improve the performance of the rotor blades, two types (KA152313 and KB203611) of airfoils were designed and compared. Methods: The nose shape of the KB203611 airfoil was ‘drooped’ and ‘sharp’ compared to the leading edge of the KA152313 airfoil. The performance of the experimental airfoils was simulated using CFD-ACE program, and lifts were measured in situusing the ‘AgroHeli-4G’, a prototype helicopter. Results: Simulated lifts of the blade with the KA152313 airfoil showed proper values for a wide range of angles of attack between 14°~18°, while the simulated lift of the KB203611 blade exhibited maximum values near 13°~14°. In the lift measurements, the range of operable angles of attack was a collective pitch angle at the grip (GP) of 12°~18° for the KA152313 blade. On the other hand, the range of angles of attack for the KB203611 blade was a GP of 12°~14°. Conclusions: The blade of KA152313 performed well over a wide range of AoAs and the blade of KB203611 performed better at low AoAs. In this study, a variative airfoil blade, gradually emerging from grip to tip using the two different airfoils, was suggested.

Design optimization of wind turbine blades for reduction of airfoil self-noise

이승훈,이수갑,이재하,최종수 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.2

To reduce airfoil self-noise from a 10 kW wind turbine, we modified the airfoil shape and planform of a wind turbine blade. To ob-tain the optimal blade design, we used optimization techniques based on genetic algorithms. The optimized airfoil was first determined based on a section of the rotor blade, and then the optimized blade was designed with this airfoil. The airfoil self-noise from the rotor blades was predicted by using a semi-empirical model. The numerical analysis indicates that the level of the airfoil self-noise from the optimized blade is 2.3 dB lower than that from the baseline blade at the rated wind speed. A wind tunnel experiment was also performed to validate the design optimization. The baseline and optimized rotors were scaled down by a factor of 5.71 for the wind tunnel test. The experimental results showed that airfoil self-noise is reduced by up to 2.6 dB.

풍력 블레이드용 익형 개발에 대한 연구

김태우(Kim, Tae-Woo),박상규(Park, Sang-Gyoo),김진범(Kim, Jin-Bum),권기영(Kweon, Ki-Yeoung),오시덕(Oh, Si-Deok) 한국신재생에너지학회 2009 한국신재생에너지학회 학술대회논문집 Vol.2009 No.06

This research describes on airfoil shape design, crucial to core technique and algorithm optimization for the wind turbine blade development. We grasped the parameter to define the airfoil shape in the wind turbine blade and aircraft, and the important performance characteristic of the airfoil. The airfoil shape function is selected by studying which is suitable for wind turbine blade airfoil development. The selected method is verified by to compare the generated airfoil shape with base airfoil. The new airfoils were created by the selecting shape function based on the well-known airfoil for wind turbine blades. In addition, we performed aerodynamic analysis about the generated airfoils by XFOIL and estimated the point of difference in the airfoil shape parameter using the aerodynamic performance results which is compared with basic airfoil. This result data applies to the fundamental research for a wind turbine blade optimization design and accomplished the aerodynamic analysis manual.

Performance Comparison of Two Airfoil Rotor Designs for an Agricultural Unmanned Helicopter

Koo, Young-Mo Korean Society for Agricultural Machinery 2012 바이오시스템공학 Vol.37 No.1

Purpose: The most important element of an agricultural helicopter is the rotor blade realizing lift force. In order to improve the performance of the rotor blades, two types (KA152313 and KB203611) of airfoils were designed and compared. Methods: The nose shape of the KB203611 airfoil was 'drooped' and 'sharp' compared to the leading edge of the KA152313 airfoil. The performance of the experimental airfoils was simulated using CFD-ACE program, and lifts were measured in situ using the 'AgroHeli-4G', a prototype helicopter. Results: Simulated lifts of the blade with the KA152313 airfoil showed proper values for a wide range of angles of attack between $14^{\circ}{\sim}18^{\circ}$, while the simulated lift of the KB203611 blade exhibited maximum values near $13^{\circ}{\sim}14^{\circ}$. In the lift measurements, the range of operable angles of attack was a collective pitch angle at the grip (GP) of $12^{\circ}{\sim}18^{\circ}$ for the KA152313 blade. On the other hand, the range of angles of attack for the KB203611 blade was a GP of $12^{\circ}{\sim}14^{\circ}$. Conclusions: The blade of KA152313 performed well over a wide range of AoAs and the blade of KB203611 performed better at low AoAs. In this study, a variative airfoil blade, gradually emerging from grip to tip using the two different airfoils, was suggested.

BEM 이론에 의한 에어포일 직접설계에 관한 연구

최철영,선민영 한국기계기술학회 2021 한국기계기술학회지 Vol.23 No.3

본 연구는 해상풍력 터빈 블레이드 에어포일 설계를 다룬다. 풍력 터빈 설계의 목표는 특정 대기 조건에서 가능한 가장 높은 출력을 얻는 것이다. 공기역학적 부하에 대한 수학적 설명으로 최적의 블레이드 형상을 결정하는 문제는 복잡하고 많은 제약과 목표를 충족해야 한다. 본 연구의 목적은 여러 기준에 따라 풍력 터빈 블레이드의 최적화를 가능하게 하는 직접 설계 방법으로 두 가지 유형의 에어포일 모델 개발이다. 블레이드 요소 운동량 이론을 기반으로 유체역학적 풍력 터빈 설계에 대한 수학적 모델을 생성하고 효율을 향상시켰다. 결과적으로, CFD 시뮬레이션을 통해 고효율 에어포일 모델을 설계했고, 실험 데이터와의 비교를 통해 검증했다. In this study, the offshore wind turbine of blade airfoil is studied and designed to obtain the highest output power under specific atmospheric conditions. The problems of the optimum shape of the blade are complex with the mathematical description of aerodynamic load and some constraints with the object. This study aims to develop two types of airfoil model by directing the designed method and a mathematical model for fluid dynamics. The blade element of momentum theory nor the mathematical model was implemented and improved on the blade airfoil. As a result, a high-efficiency airfoil model was designed through CFD simulation and verified by comparison with experimental data.

Optimization of thick wind turbine airfoils using a genetic algorithm

정재호,김수현 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.7

In this study, we optimized thick airfoils for wind turbines using a genetic algorithm (GA) coupled with computational fluid dynamics (CFD) and geometric parameterization based on the Akima curve fitting method. Complex and separated flow fields around the airfoils of each design generation were obtained by performing Reynolds-averaged Navier-Stokes steady flow simulation based on the in-house code of an implicit high-resolution upwind relaxation scheme for finite volume formulation. Airfoils with 40 % and 35 % thickness values were selected as baseline airfoils. An airfoil becomes thicker toward the blade root area, thereby increasing blade stiffness and lowering its aerodynamic efficiency. We optimized the airfoils to simultaneously maximize aerodynamic efficiency and blade thickness. The design variables and objective function correspond to the airfoil coordinates and the lift-to-drag ratio at a high angle of attack with airfoil thickness constraints. We improved the lift-to-drag ratio by 30 %~40 % compared with the baseline airfoils by performing optimization using GA and CFD. The improved airfoils are expected to achieve a 5 %~11 % higher torque coefficient while minimizing the thrust coefficient near the blade root area.

2.5MW급 블레이드 설계 및 전산해석에 관한 연구

염슬기(Seul-Ki Yeom) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.8

국내에서는 한정적인 자원으로 장기적인 관점에 고갈되어 가기 때문에 대체자원에 대한 관심이 높아지고 있다. 신재생에너지 중에서 풍력에너지에 대한 연구 및 제도가 시행되고 있다. 10kw급과 같은 소형에서부터 20MW급의 대형 해상풍력발전기까지 지속적으로 개발되고 있다. 풍력발전기 블레이드의 설계를 위해 BEM 이론을 통한 공력설계, 수직축 및 수평축 블레이드 설계, 실제 풍력시험을 통한 공력성능 검증, GH-Bladed를 통한 시스템적 해석 등을 연구해왔다. 본 논문에서는 NREL 5MW급 풍력발전기 시스템에 적용된 에어포일 시리즈를 선정하여 2.5MW급 수평축 풍력발전기 설계를 진행하였다. 블레이드의 기본적인 설계를 위해 Blade Element Momentum(깃 요소) 이론을 적용하였으며, 블레이드 길이와 정격 회전속도를 통해 각 코드길이와 비틀림 각을 설정하였다. 이 때 에이포일은 DU시리즈와 NACA64-618을 적용하여 두께분포에 따라 구성하였다. 이를 3D 프로그램인 CATIA로 블레이드 한쪽 날개를 설계한 뒤 ANSYS Fluent를 통해 전산유체해석을 진행하였다. 전체 유동장은 점성 비압축성 Navier-stokes를 적용하고, 난류모델은 정상상태로 Spalart-allmaras을 적용하였다. 유동해석의 시간을 줄이기 위해 서로 다른 좌표계들을 이용하여 블레이드 회전을 고려하는 Multiple Reference Frame(MRF)을 통해 진행하였다. 해당 해석기법을 통해 한 개의 블레이드 값으로 블레이드 전체의 값을 도출하였다. 그 결과, 정격회전속도인 12.17rpm에서 약 2.6MW급 출력을 나타내었다. 이를 통해서 각 요소들을 통해 정격출력에 도달함을 확인하였다. In South Korea, interest in alternative resources is increasing as they are depleted from a long-term perspective with limited resources. Research and systems for wind energy are being implemented as new and renewable energy. Wind energy is continuously being developed from a small size such as the 10-kW class to large offshore wind power generators of the 20-MW class. For the design of wind turbine blades, aerodynamic design has been studied through blade element moment theory, vertical and horizontal axis blade design, aerodynamic performance verification through wind tests, and systematic analysis through GH Bladed. In this study, an airfoil series applied to an NREL 5-MW wind power generator system was selected, and a 2.5-MW horizontal axis wind power generator was designed. For the basic design of the blade, blade element moment theory was applied, and each cord length and twist angle were set through the blade length and rated rotational speed. The airfoil was constructed according to the thickness distribution by applying the DU series and NACA64-618. After designing one wing of the blade with the CATIA 3D program, computational fluid analysis was conducted through the ANSYS Fluent program. The entire flow field was applied with viscous incompressible Navier-Stokes equations, and the Spalart-Allmaras turbulence model was applied in a normal state. In order to reduce the time for flow analysis, it was conducted through multiple reference frames (MRFs), which consider blade rotation using different coordinate systems. Through this analysis technique, the value of the entire blade was derived with one blade value. As a result, the output was about 2.6 MW at a rated rotation speed of 12.17 rpm. It was confirmed that the rated output was reached through each element.

풍력블레이드용 에어포일세트의 설계 및 해석

신형기(Shin, Hyung-Ki),김석우(Kim, Seok-Woo) 한국신재생에너지학회 2007 한국신재생에너지학회 학술대회논문집 Vol.2007 No.06

In wind turbine blades, airfoils are required to have different spec when compared with airplane airfoil. Airfoils for wind turbine blade must have a high lift-to-drag ratio, moderate to high lift and especially low roughness sensitivity. Also an operation Re. No.s are lower than conventional airplane airfoils. At mid-span and inboard region, structural problems have to be considered. Especially, for stall regulated type, moderate stall behavior is essential part of design. For these reasons, airfoil design for HAWT blade is essential part of blade design. In this paper, root airfoil and tip airfoil are discussed. For a root region, 24% thickness airfoil is designed and for a top region, 12% thickness ratio is done. A inverse design method and panel method are used for rapid airfoil design. In this paper, a design method, features of airfoil shape and characteristics are discussed.