High-temperature oxidation of a Ni-based superalloy was analyzed with samples taken from gas turbine blades, where the samples were heat-treated and thermally exposed. The effect of Cr/Ti/Al elements in the alloy on high temperature oxidation was investigated using an optical microscope, SEM/EDS, and TEM. A high-Cr/high-Ti oxide layer was formed on the blade surface under the heat-treated state considered to be the initial stage of high-temperature oxidation. In addition, a PFZ (γ’ precipitate free zone) accompanied by Cr carbide of Cr23C6 and high Cr-Co phase as a kind of TCP precipitation was formed under the surface layer. Pits of several μm depth containing high-Al content oxide was observed at the boundary between the oxide layer and PFZ. However, high temperature oxidation formed on the thermally exposed blade surface consisted of the following steps: ① Ti-oxide formation in the center of the oxide layer, ② Cr-oxide formation surrounding the inner oxide layer, and ③ Al-oxide formation in the pits directly under the Cr oxide layer. It is estimated that the Cr content of Ni-based superalloys improves the oxidation resistance of the alloy by forming dense oxide layer, but produced the σ or μ phase of TCP precipitation with the high-Cr component resulting in material brittleness.

로터 블레이드는 조류발전 터빈의 매우 중요한 구성 요소로서, 해수의 높은 밀도로 인해 큰 추력(Trust force)와 하중(Load)의 영 향을 받는다. 따라서 블레이드의 형상 및 구조 설계를 통한 성능과 복합소재를 적용한 블레이드의 구조적 안전성을 반드시 확보해야 한 다. 본 연구에서는 블레이드 설계 기법인 BEM(Blade Element Momentum) 이론을 이용해 1MW급 대형 터빈 블레이드를 설계하였으며, 터빈 블레이드의 재료는 강화섬유 중의 하나인 GFRP(Glass Fiber Reinforced Plastics)를 기본으로 CFRP(Carbon Fiber Reinforced Plastics)를 샌드위치 구조에 적용해 블레이드 단면을 적층(Lay-up)하였다. 또한 유동의 변화에 따른 구조적 안전성을 평가하기 위해 유체-구조 연성해석 (Fluid-Structure Interactive Analysis, FSI) 기법을 이용한 선형적 탄성범위 안의 정적 하중해석을 수행하였으며, 블레이드의 팁 변형량, 변형 률, 파손지수를 분석해 구조적 안전성을 평가하였다. 결과적으로, CFRP가 적용된 Model-B의 경우 팁 변형량과 블레이드의 중량을 감소시 켰으며, 파손지수 IRF(Inverse Reserce Factor)가 Model-A의 3.0*Vr를 제외한 모든 하중 영역에서 1.0 이하를 지시해 안전성을 확보할 수 있었 다. 향후 블레이드의 재료변경과 적층 패턴의 재설계뿐 아니라 다양한 파손이론을 적용해 구조건전성을 평가할 예정이다.

In this study, defects generated in the YSZ coating layer of the IN738LC turbine blade are investigated using an optical microscope and SEM/EDS. The blade YSZ coating layer is composed of a Y-Zr component top coat layer and a Co component bond coat layer. A large amount of Cr/Ni component that diffused from the base is also measured in the bond coat. The blade hot corrosion is concentrated on the surface of the concave part, accompanied by separation of the coating layer due to the concentration of combustion gas collisions here. In the top coating layer of the blade, cracks occur in the vertical and horizontal directions, along with pits in the top coating layer. Combustion gas components such as Na and S are contained inside the pits and cracks, so it is considered that the pits/cracks are caused by the corrosion of the combustion gases. Also, a thermally grown oxide (TGO) layer of several μm thick composed of Al oxide is observed between the top coat and the bond coat, and a similar inner TGO with a thickness of several μm is also observed between the bond coat and the matrix. A PFZ (precipitate free zone) deficient in γ' (Ni3Al) forms as a band around the TGO, in which the Al component is integrated. Although TGO can resist high temperature corrosion of the top coat, it should also be considered that if its shape is irregular and contains pore defects, it may degrade the blade high temperature creep properties. Compositional and microstructural analysis results for hightemperature corrosion and TGO defects in the blade coating layer used at high temperatures are expected to be applied to sound YSZ coating and blade design technology.

Numerical analysis for flow and noise characteristics of sirocco fan design factors is conducted in this study. 4 cases of blade angle(α=24°~30°) and 5 cases of RPM(390~1170RPM) are calculated. Flow characteristics are compared for the number of blades. Outlet flow rate is tended to decrease as the number of blades increased. There is little difference in the flow characteristics for the angle of blade. The highest outlet flow rate is predicted at α=24°, and the lowest at α=28°. Flow and noise characteristics are compared for α=24° and 26°. Outlet flow rate is almost similar in both cases, but noise for α=24° is predicted higher at high RPM conditions.

블레이드는 바람 에너지를 전기 에너지로 변환하기 위한 풍력발전기 시스템의 핵심 요소이다. 블레이드의 공기역학적 설계는 적절한 에어포일을 선택하고 블레이드 축을 따라 최적의 단면을 결정하는 것이다. 본 연구의 목표는 블레이드 에어포일의 모델을 개발하고, 개발한 에어포일의 효율을 분석하는 것이다(블레이드 형상은 수정된 SM 시리즈 프로파일을 기반으로 함). 일반적으로 풍력 터빈 블레이드는 Cl/Cd에 민감하다. 본 연구의 초점은 X-Foil 프로그램을 통해 강한 바람과 돌풍에서의 최고 효율(Cl/Cd)을 위한 에어포일의 좌표를 최적화시키는 것이다. 국내 해역의 난류 특성, 돌풍 및 바람 조건에 대한 적절한 에어포일을 개발하기 위해서는 수치 해석을 통해 에어포일의 길이와 이에 따른 두께비(Y/C), 에어포일의 최대 두께비에 대한 상대 위치(Xd), S형 tail edge 및 비율 등을 계산하여 결정한다. X-Foil 프로그램을 통해 모델링된 2D 모델에 대하여 CFD(Computational Fluid Dynamics) 검증을 반복 수행하여 최적화시켰다.

블레이드 개발에서 매우 중요한 요소는 에어포일 설계이다. 본 연구에서는 DesignFoil 프로그램을 통한 에어포일의 최적화에 관한 연구를 다룬다. 이를 위해, NACA 4-digit series 및 5-digit series 공식을 이용하여 좌표 값을 도출시키고, 이를 통해 구해진 초기 단면형상을 DesignFoil 프로그램에 입력시킨 뒤, 각 매개 변수(피칭 모멘트, 레이놀즈 수, 마하 수, 두께 비율 및 받음각)에 대하여 양력 대 항력 비율을 최적화시켰다. 그 결과, 에어포일 단면 좌표를 최적화시키고, VisualFoil 프로그램을 통해 에어포일의 성능을 확인하고 블레이드 형상을 결정했다.

The wind turbine blades should be designed to possess a high stiffness and should be fabricated with a light and high strength material because they serve under extreme combination of lift and drag forces, converting kinetic energy of wind into shaft work. The goal of this study is to understand the basic knowledge required to curtail the process time consumed during the construction of small wind turbine blades using carbon fiber reinforced polymer (CFRP) prepeg composites. The configuration of turbine rotor was determined using the QBlade freeware program. The fluid dynamics module simulated the loads exerted by the wind of a specific speed, and the stress analysis module predicted the distributions of equivalent von Mises stress for representing the blade structures. It was suggested to modify the shape of test specimen from ASTM D638 to decrease the variance in measured tensile strengths. Then, a series of experiments were performed to confirm that the bladder compression molded CFRP prepreg can provide sufficient strength to small wind turbine blades and decrease the cure time simultaneously.

정공 수송 층 (HTL)은 PSC의 효율 및 안정성을 증가시키기 위해 페로브스카이트 태양 전지 (PSC)에서 중요한 역할을 한다. 본 연구에서, 우리는 PSCs에서 HTL 스핀 코팅 및 블레이드 코팅 방법으로 니켈 산화물 구리 산화물 (NiO-CuO) 나노 입자 (NPs) 박막을 준비하였다. 스핀 코팅 및 블레이드 코팅 된 NiO-CuO 필름의 필름 특성은 원자력 현미경 (AFM)을 사용하여 조사하었고, 장치 성능에 대한 효과는 J-V 특성, 양자 효율 및 광 강도의 Voc 의존성을 사용하여 조사하었다. 결과적으로, 스핀 코팅으로 15.28 % 효율, 블레이드 코팅으로 11.18 % 효율을 달성하였다.

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.

An icing phenomenon of wind turbine blade are caused by wind speed, air temperature, liquid water content, droplet size, and so on. In this study, the analyses were carried out at a liquid water content of 0.20g/㎥, droplet size of 25 um, wind speed of 11.4m/s and air temperatures of -15, -10, -5℃ using NREL 5MW wind turbine. The software uses FENSAP-ICE's CFD Flow Solver, Drop 3D and ICE 3D. The analysis of icing shape and mass with temperatures according to air foil was derived, and the required heat quantity for de-icing was calculated at NACA 64618 airfoil for air temperature of -15℃. Power curves with wind velocities are suggested for economical analysis.

This study is to conduct the optimal design of the fluid mixing blades in the test fluid tank for sewage treatment process. The design was made with various shapes and angles of mixing blades. Fluid mixing blades in the tank are numerically analyzed with FLUENT V.13.0. Blade1 and Blade4 had the biggest fluid pressure difference of 8.1% around the blades. And, Blade1 and Blade3 had the least fluid pressure difference of 2.55%. The biggest turbulence kinetic energy of 12.5% existed around Blade1 and Blade4. Blade1 and Blade3 had the least turbulent kinetic energy difference of 4.8%. Blade4 is the optimal design shape due to the highest turbulent kinetic energy around the blades in comparison to the other cases.