多种载荷作用下H型垂直轴风力机叶片的结构优化

为改善时变载荷下H型垂直轴风力机叶片的结构性能,通过FSI映射准确、实时地提取气动力并进行多种荷载耦合作用时的多目标结构优化设计。分别应用解析法和有限元法求解构件弯曲变形的应力分量与强度比,比较计算结果验证有限元分析过程的正确性。将坐标旋转变换和缩放横纵坐标系数相结合进行NACA0021翼型尾缘改型,并使翼型中弧线位于风轮圆周上,获得有弯度的尖尾缘翼型NACA0021SC。利用APDL语言建立新翼型叶片的参数化模型,采用FLUENT软件计算其表面实时压力分布,基于FSI映射方法获得气动力。以叶片的质量最小同时层合板强度比最大为设计目标,利用惯性权重余弦自适应和学习因子动态调整改进粒子群算法,进行重力、离心力、气动力共同作用下叶片结构的多目标优化。结果表明:单叶片在各方位角下优化后,质量分别减小13.70%,11.85%,8.09%和9.60%,最大位移、最大应力、最大应变和强度比倒数的最大降幅为9.34%、20.71%、23.77%、9.38%;风轮优化后,质量、最大位移、最大应力、最大应变和强度比倒数最大值减小7.51%、1.90%、8.50%、20.20%和16.11%。研究结论可为风力机叶片在考虑时变载荷影响下的结构优化设计提供指导。

Structural optimization of H-type vertical axis wind turbine blade under multi-loads

Abstract: The larger stress and strain concentration will be caused in some positions of the blade by the coupling action of gravity, centrifugal force and aerodynamic load in the rotation process, which can reduce the reliability and life of wind turbine. Most of the blades with hollow thin-walled structure are made of glass fiber reinforced composite material, and the optimal design of internal structure and fiber layer is used to improve the strength and rigidity. Furthermore, the aerodynamic force that is the main power source changes with the wind speed all the time. Therefore, it is of great theoretical significance of guidance and engineering value of application to perform the accurate and real-time extraction of aerodynamic force, and optimize structural geometry parameters and composite layer for the blade under the coupling effects of multiple loads. The optimization can ensure safe and stable operation of wind turbine. However, the investigation about the structural optimization of vertical axis wind turbine (VAWT) blade considering the time-varying load effect is few. In the present study, the multi-objective structural optimization design of the blade was performed to improve the structural performance of H-type VAWT when the multi-loads were coupled. First, the transverse stress, longitudinal stress, shear stress and strength ratio under the bending deformation of beam whose constraints and forces were similar to those of the blade, were obtained by analytical and finite element methods. The results of two methods were compared to verify the correctness of finite element analysis process. Moreover, the trailing-edge of NACA0021 airfoil was modified with the coordinate rotation and coefficient zoom, and then the airfoil''s middle arc line located on the circumference of wind wheel. The sharp tailing-edge airfoil with certain camber, namely NACA0021SC, was obtained. Furthermore, the parametric finite element model of the blade with new airfoil was established with the APDL language. The pressure distribution on the blade surface was calculated by FLUENT, and the aerodynamic force extracted accurately and in real-time by the FSI mapping method was applied on mesh elements of the blade structure to realize the aerodynamic force transfer between FLUENT and ANSYS. Finally, the particle swarm optimization (PSO) algorithm, which was improved through the cosine adaptive of inertia weight and dynamic adjustment of learning factor, was applied for the structural optimization by taking the minimum blade mass and maximum laminate strength ratio as design objectives. The results showed that the mass of single blade at different azimuth angles of 90°, 180°, 270° and 360° decreased by 13.70%, 11.85%, 8.09% and 9.60% after optimization, respectively. The maximum stress and strain decreased by as much as 20.71% and 23.77% at the azimuth angles of 90° and 180°, the biggest decline of maximum displacement was 9.34% at the azimuth angle of 360°, and the reciprocal of strength ratio reduced mostly at the azimuth angle of 180° by 9.38%. To the wind turbine, the mass, maximum stress, maximum strain, maximum displacement, and maximum reciprocal of strength ratio decreased by 7.51%, 8.50%, 20.20%, 1.90% and 16.11%, respectively. The stress concentration and deformation decreased and the strength increased, which indicated that the structural performance was enhanced. The research can provide significant guidance for structural optimization of wind turbine blade with time-varying load.