• Composites Research
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• 제29권6호
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• pp.369-374
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• 2016

본 연구에서는 굽힘-비틀림 커플링(bend-twist coupled, BTC) 설계개념을 적용한 10 MW급 복합재 풍력 블레이드의 구조 최적 설계를 수행하였다. BTC 설계개념은 동적 하중 상황에서 블레이드의 굽힘과 비틀림 거동 사이의 연동을 유도하여, 단면 받음각 변화에 의한 수동적인 적응 하중저감이 가능하다. 인자연구를 통해 최적의 BTC 설계인자를 추출하여 블레이드 구조설계에 적용하였다. BTC 개념이 동적 하중 감소에 미치는 영향을 가늠하기 위해 블레이드 루트 부에서의 피로등가하중을 계산한 결과, BTC 개념이 적용된 블레이드를 적용한 경우 피로등가하중이 2-3% 정도 감소하는 것을 확인할 수 있었다. BTC 효과를 시험적으로 검증하기 위해 1:29 비율의 블레이드 stiffener 축소모델을 제작하였으며, 정하중 시험을 통해 처짐 거동 시 끝단에서의 비틀림을 측정하였다.

• 대한기계학회논문집B
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• 제21권7호
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• pp.911-918
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• 1997

The turbulent viscous wake flows behind a single airfoil, two-dimensional stationary blade row and three-dimensional rotating blade row were calculated, and the numerical results were compared with experimental ones. The numerical technique was based on the SIMPLE algorithm using three turbulent closure models, standard k-.epsilon. model(WFM), low Reynolds number k-.epsilon. model(LRN) and Reynolds stress model (RSM). In the case of a single airfoil, WFM, LRN and RSM presented fairly good velocity distributions in the wake compared with experimental data. In the case of the stationary blade row, LRN and RSM presented better results than WFM for wake velocity distribution, and especially LRN showed best results among these three turbulent models. In the case of the rotating blade row, WFM and LRN showed fairly good agreement with experimental data of the three-dimensional velocity component distributions in the range from hub to mid span region. LRN was also superior to WFM in accuracy of prediction for the wake velocity distribution as same with the cases of a airfoil and the stationary blade row.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.33-36
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• 2005

A critical issue in the field of the rotor aerodynamics is the treatment of the wake. The wake is of primary importance in determining overall aerodynamic behavior, especially, a wind turbine blade includes the unsteady air loads problem. In this study, the wake generated by blades are depicted by a free wake model to analyse unsteady loading on blade and a new free wake model named Finite Vortex Element(FVE hereafter) is devised in order to include a wake-tower interact ion. In this new free wake model, blade-wake-tower interaction is described by cutting a vortex filament when the filament collides with a tower. This FVE model is compared with a conventional free wake model and verified by a comparison with NREL and SNU wind tunnel model. A comparison with NREL and SNU data shows validity and effectiveness of devised FVE free wake model and an efficient.

• 한국소음진동공학회논문집
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• 제22권7호
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• pp.659-666
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• 2012

A nonlinear dynamic model for the shaft-disk-blade unit is developed in this study. In this regard, the rotating flexible blade, with a pre-twist angle, attached to a rigid disk driven by a shaft which is flexible in torsion is developed. The rotor-blade coupled model is derived using Lagrange equation in conjunction with the assumed mode method to discretize the blade deformation. The equations of motion are analyzed based on the small deformation theory for the blade and shaft torsional deformation to obtain the system natural frequencies for various system parameters.

• 한국유체기계학회 논문집
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• 제17권4호
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• pp.19-29
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• 2014

In addition to the development of micro hydro turbine, the challenge in micro hydro turbine design as sustainable hydro devices is focused on the optimization of turbine runner blade which have decisive effect on the turbine performance to reach higher efficiency. A multi-objective optimization method to optimize the performance of runner blade of propeller turbine for micro turbine has been studied. For the initial design of planar blade cascade, singularity distribution method and the combination of the Bezier curve parametric technology is used. A non-dominated sorting genetic algorithm II(NSGA II) is developed based on the multi-objective optimization design method. The comparision with model test show that the blade charachteristics is optimized by NSGA-II has a good efficiency and load distribution. From model test and scale up calculation, the maximum prototype efficiency of the runner blade reaches as high as 90.87%.

• Wind and Structures
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• 제29권6호
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• pp.431-440
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• 2019

The aim of this study was to explore the influence of structure coupling effect on structural damping of blade based on the blade vibration characteristic. For this purpose, the scaled blade model of NREL 5 MW offshore wind turbine was processed and employed in the wind tunnel test to validate the reliability of theoretical and numerical models. The attenuation curves of maximum displacement and the varying curves of equivalent damping coefficient of the blade under the rated condition were respectively compared and analyzed by constructing single blade model and whole machine model. The attenuation law of blade dynamic response was obtained and the structure coupling effect was proved to exert a significant influence on the equivalent damping coefficient. The results indicate that the attenuation trend of the maximum displacement response curve of the single blade varies more obviously with the increase of elastic modulus as compared to that under the structure coupling effect. In contrast to the single blade model, the varying curve of equivalent damping coefficient with the period is relatively steep for the whole machine model. The findings are of great significance to guide the structure design and material selection for wind turbine blades.

• 한국유체기계학회 논문집
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• 제14권3호
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• pp.39-44
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• 2011

In this study, performance analyses have been conducted for a 5MW class wind turbine blade model. Advanced computational analysis system based on computational fluid dynamics(CFD) and computational structural dynamics(CSD) has been developed in order to investigate detailed dynamic responsed of wind turbine blade. Reynolds-averaged Navier-Stokes (RANS) equations with K-${\epsilon}$ turbulence model are solved for unsteady flow problems of the rotating turbine blade model. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3D turbine blade for fluid-structure interaction (FSI) problems. Predicted aerodynamic performance considering structural deformation effect of the blade show different results compared to the case of rigid blade model.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.729-734
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• 2001

A 3-dimentional finite element model for vibration analysis of steam-turbine blade groups is presented, employing the 3-dimentional incompatible brick element with 8 nodes. The skew coordinate system is introduced in the model for considering multi-axis symmetry and specialty of displacement constrain condition of blade groups. Vibration characteristics of blade groups are analyzed, and compared with experimental results.

• 한국기계기술학회지
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• 제20권6호
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• pp.844-851
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• 2018

In this study, the regression equation was suggested to predict of the shot ball velocity according to blade shapes based on discrete element (DE) analysis. First, the flat type blade DE model was used in the analysis, the validity of the DE model was verified by giving that the velocity of the shot ball almost equal to the theoretical one. Next, the DE analyses for curved and combined blade models was accomplished, and their analytical velocities of shot ball were compared with the theoretical one. The velocity of combined blade model was greatest. From this, the regression equation for velocity of shot ball according to the blade shape based on the DE analysis was derived. Additionally, the wind speed measurement experiment was carried out, and the experimental result and analytical one were the same. Ultimately, it was confirmed that the prediction method of the velocity of shot ball based on DE analysis was effective.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.571-580
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• 2015

In this paper, a computational study was conducted in order to investigate the rotor blade sweep effect on the aerodynamics of a small axial supersonic impulse turbine stage. For this purpose, three-dimensional unsteady RANS simulations have been performed with three different rotor blade sweep angles ($-15^{\circ}$, $0^{\circ}$, $+15^{\circ}$) and the results were compared with each other. Both NTG (No tip gap) and WTG (With tip gap) models were applied to examine the effect on tip leakage flow. As a result of the simulation, the positive sweep model ($+15^{\circ}$) showed better performance in relative flow angle, Mach number distribution, entropy rise, and tip leakage mass flow rate compared with no sweep model. With the blade static pressure distribution result, the positive sweep model showed that hub and tip loading was increased and midspan loading was reduced compared with no sweep model while the negative sweep model ($-15^{\circ}$) showed the opposite result. The positive sweep model also showed a good aerodynamic performance around the hub region compared with other models. Overall, the positive sweep angle enhanced the turbine efficiency.