低温结冰环境下水平轴风力机叶片设计理论及颤振机理研究

The wind power, with the characteristic of low cost and zero pollution, has been favored by the countries around the world. The performance of the wind turbine blades in our country is obviously influenced by the work environment. Taking the low temperature and icing environment as the starting point, this project researches on the flutter phenomenon caused of the blade damage as well as the efficiency of wind turbine blades reducing caused by icing, using the numerical simulation and experimental methods. A blade design theory is proposed for low temperature and icing environments, which could get three dimensional wind turbine blades for adapting to the cold environment with using inverse design technology design, computational fluid dynamics technology, optimization design technology and Wilson theory. The research on the calculation method of blades vibration based on dynamic mesh will carry out，to provide computational tools for blades flutter study. The research on blades vibration will carry out under different conditions, analyzing the cause for flutter generation and studying on the mechanism. The research on the flutter experiment will carry out, to verify the correctness of the design method and calculation method. A blade design system would be proposed which not only ensures the blade aerodynamic performance but also improves the security of blades. The research will reveal the mechanism of the fluid-structure interaction between the actual flow field of wind turbine and the blades in the unsteady incompressible at low temperature, raising awareness of blade flutter mechanism, drawing control methods for flutter at low temperature, improving the security of blades, so that provide a theoretical basis for the independent design of large-scale wind turbine.

风力以成本低，零污染的特点受到世界各国的青睐，而我国风力机叶片工作性能受环境影响较为明显。本项目以低温结冰环境为出发点，针对引起叶片破坏的颤振现象及覆冰导致风力机叶片效率下降的问题，采用数值模拟与实验方法开展相关研究。提出一种适用于低温结冰环境的叶片设计理论，该理论利用反设计技术、计算流体力学技术、优化设计技术及Wilson理论获取适应低温环境的三维风力机叶片。开展基于动网格技术的叶片振动计算方法研究，为叶片颤振研究提供计算工具。在不同工况下对叶片振动现象开展研究，捕获分析颤振现象，阐明颤振机理。开展叶片颤振实验研究，验证设计方法及计算方法正确性，建立既保证叶片气动性能又提高叶片安全性的叶片设计体系。研究工作将揭示非定常不可压低温条件下的风力机实际流场与叶片的流固耦合作用机理，提高对叶片颤振机理的认识，给出低温条件下颤振控制方法，提高叶片安全性，为大型风力机的自主设计提供理论基础。

为提高低温环境风力机叶片抗冰性能和安全性，利用计算流体力学方法和优化设计等技术获取适应低温环境的三维风力机新型叶片。设计了两种新型叶片Blade A、Blade B，分析了风力机叶片在风速和来流角度等不同条件下的结冰特性。研究发现，叶片主要结冰区域为翼型的迎风面前缘、尾缘和叶片的中轴区。两种新型叶片均具有良好的抗冰特性,新型叶片Blade A抗冰性能更为优越。在9m/s风速下新型叶片Blade A结冰量相比原型叶片结冰量要减少5.51%，在12m/s风速下结冰量减少1.94%；在3°来流角下结冰量减少4.99%，在5°来流角下结冰量减少4.43%，研究还发现温度对风力机结冰特性影响较大。利用动网格技术捕获了平板和翼型的颤振现象，与解析解结果一致，验证了流固耦合技术用于风力机叶片振动分析的可行性。开展了风力机叶片振动特性研究及振动试验测量工作。首先分析转速及风速改变对风力机叶片振动的影响，转速及风速的增大导致叶片起振阶段的最大振幅值变大，振幅数值呈线性增长关系。随后对新型叶片开展了颤振问题研究，当叶片发生颤振现象时，振动曲线呈发散趋势，叶根处的应力会逐步增加，如不加以抑制则会导致叶片破坏，研究发现在叶片内部增加纵梁和横梁可抑制颤振现象发生。对比不同材料的风力机叶片振动位移曲线，发现碳纤维叶片相较于玻璃纤维叶片具备更好的抗振特性。最后，研究新型叶片覆冰状态下的振动特性，得益于良好的气动设计，覆冰叶片起振振幅小于原型未覆冰叶片的起振振幅。上述研究表明，所设计的叶片具有较好的抗冰性及抗振性，可为寒冷地区大型风力机叶片设计研究提供理论基础。