基于风洞试验15 MW风力机叶片颤振后形态与能量图谱研究

Experimental study on the post-flutter morphological chracteristics and energy dissipation of a 15 MW wind turbine blade

现有风力机叶片颤振分析大多关注颤振临界状态预测,忽略了非线性更为显著的颤振后形态和能量耗散。本文基于变分渐进梁截面法设计了新型超长柔性叶片气动-刚度-质量映射一体化三维弹性模型,采用高速摄像技术和高频六分量天平进行了同步测振、测力风洞试验,分析了风力机叶片颤振敏感风向区间与临界风速组合规律,最后基于叶尖风振响应、气动阻尼和能量,系统研究了风振敏感工况风振响应下风力机叶片能量演变规律和颤振临界风速后的形态特性,揭示了风力机叶片颤振后能量耗散机制。研究表明:提出的风力机叶片弹性模型设计和试验方法能有效模拟结构动力性能与颤振行为;风力机叶片的桨距角93°~96°和284°~286°区间属于风振敏感区间,在该区间内超过临界风速即可发生大幅锁频振动;存在能量积累突变界线,超过该界线对应风速后的能量积累尤为显著,表现出风致振动能量随时间呈现显著的非平稳特性;颤振后气动负阻尼是结构系统发散的主要原因。

Most existing flutter analyses of wind turbine blades focus on predicting critical flutter states.While the post-flutter morphological evolution and the associated energy dissipation,well-known for the prominent non-linear effect,are usually ignored.To characterize this non-linear phenomenon,a threedimensional aeroelastic model of ultra-long flexible blades is proposed using the variational progressive beam section method.And synchronous measurements of vibration and force are carried out in a wind tunnel using high-speed cameras and a high-frequency six-component balance.The flutter sensitivity of wind turbine blades to the wind direction and speed is firstly analyzed.Later,the post-flutter morphological characteristics and the energy dissipation of wind turbine blades subjected to wind-induced vibration are systematically studied.Results indicate that the proposed aeroelastic model and the experimental method can effectively capture the post-flutter dynamic process.The pitch angles of wind turbine blades prone to the wind-induced vibration fall in two ranges,namely 93°~96°and 284°~286°,in which high-frequency locking vibrations can occur beyond the critical wind speed.At the same time,the energy accumulation becomes particularly significant at higher wind speeds,indicating that the wind-induced vibrations are non-stationary.The negative post-flutter aerodynamic damping is the main reason for the divergence of structural systems.