The present study was conducted to evaluate the analytical precision of finite element analysis models of wind turbine bearings. In the finite element analysis models, balls were modeled as finite element meshes as a solid model or replaced by nonlinear springs as two kinds of spring models. In addition, test bench modeling was performed to calculate the displacement following the application of a turnover moment by means of a global model analysis and to calculate the contact stress by means of a sub-model analysis. The comparison of the results of the finite element analyses with the results of the bearing bench test showed that the analytical precision was 17% in the single-spring model, 9% in the Daidie spring model, and 3% in the finite element mesh ball model, indicating that the finite element mesh ball model exhibited the highest precision.

In this study, a resonance avoidance control algorithm was designed to address the tower resonance problem of a semi-submersible floating offshore wind turbine (FOWT) and the dynamic performance of the wind turbine, floater platform, and mooring lines at two exclusion zone ranges were evaluated. The simulations were performed using Bladed, a commercial software for wind turbine analysis. The length of simulation for the analysis of the dynamic response of the six degrees of freedom (DoF) motion of the floater platform under a specific load case was 3600 s. The simulation results are presented in terms of the time domain, frequency domain, and using statistical analysis. As a result of applying the resonance avoidance control algorithm, when the exclusion zone range was ±0.5 rpm from the resonance rpm, the overall performance of the wind turbine was negatively affected, and when the range was sufficiently wide at ±1 rpm, the mean power was reduced by 0.04%, and the damage equivalent load of the tower base side–side bending moment was reduced by 14.02%. The tower resonance problem of the FOWT caused by practical limitations in design and cost issues can be resolved by changing the torque control algorithm.

본 연구는 대형 풍력 발전기의 3열 롤러 피치 베어링의 개발과 보급이 확대됨에 따라 롤러 끝단의 응력집중, 즉 엣지 로딩으로 인한 피치 베어링의 조기 파손의 문제를 해결하기 위해 수행하였다. 이를 위해 인접 구조물의 강성과 변형을 고려한 3열 롤러 피치 베어링의 하중 분포를 유한요소 해석을 통하여 분석하였다. 그리고 롤러의 엣지 로딩 여부를 파악하기 위하여 ISO/TS 16281에 따른 라미나(Lamina model)모델을 활용 및 유한요소 해석으로 롤러 프로파일에 따른 접촉응력과 엣지 로딩 여부를 비교하였다. 그 결과 롤러의 구름면 전체가 로그 함수 형태의 프로파일 (Full logarithmic profile)을 가진 형상이 최적의 롤러 프로파일임을 확인하였다.

The performance of gas film face seals is substantially affected by the geometric features of the texture on the seal face. To enhance the design of elliptical groove face seals for efficient bidirectional rotation, a comprehensive theoretical analysis of how key parameters influence bidirectional working performance is performed, and the optimal geometric configuration is identified. The gas Reynolds equation is solved via the finite difference method to numerically assess the influence of operating parameters, including linear velocity and medium pressure, and geometric parameters, including slenderness ratio, number of grooves, and groove radius, on gas film stiffness, leakage rate, and hydrodynamic opening rate. The results demonstrate that for inclined elliptical grooves, both gas film stiffness and hydrodynamic opening rate under positive rotation are significantly higher than those under negative rotation, resulting in increased sealing leakage. With increasing rotational speed, the gap in performance between the two directions of rotation widens progressively. Elevated medium pressure leads to a deterioration in hydrodynamic opening performance. Notably, a 90° elliptical groove gas film face seal exhibits superior bidirectional rotational characteristics. Moreover, an open and incomplete groove profile is recommended for enhanced performance, provided that the degree of incompleteness is maintained within rational engineering limits. To further improve the hydrodynamic opening performance, wider ranges of numbers of grooves and slenderness ratios may be employed, with optimal performance being achieved when the number of grooves is between 8 and 16 and the slenderness ratio is between 3 and 5.