考虑结冰质量与刚度影响对风力机叶片模态分析

RESEARCH ABOUT THE EFFECT OF ICING STIFFNESS AND MASS ON THE MODE OF LARGE WIND TURBINE BLADE

为防止结冰叶片因气流影响而可能产生的振动破坏,需要了解结冰状态下叶片的自振特性。为此,考虑叶片材料的各向异性,建立了某46.5 m叶长的大型风力机叶片在有、无结冰状态下的模型,具体考虑无冰、结冰质量影响下的均匀与不均匀结冰工况、结冰质量与刚度共同影响下的均匀与不均匀结冰工况等五种工况,并分别进行有限元模态分析,得到各种工况下的前两阶挥舞与摆振、第1阶扭转模态,通过模态置信判据方法进一步对比分析结冰对其模态的影响。结果表明:结冰会造成叶片质量增加,进而频率降低,其中第1阶挥舞频率降低最大约47.79%;而结冰也会造成叶片刚度增加,进而频率增大,其中第1阶扭转频率增长最大约39.51%;叶片各阶挥舞与摆振振型受结冰影响较小,而对叶片30 m^46.5 m范围内的扭转振型影响较大,其中均匀结冰叶片第1阶扭转振型受结冰影响最为明显。

In order to prevent from catastrophic destruction when the iced blade is disturbed by the flow,the dynamic characteristics of the blade with or without icing are analyzed by using ANSYS to model a 46.5 m blade.In specific,first two-order flap-wise and lag-wise modes and first-order torsional mode are calculated,which are under five kinds of working conditions of the blade including ice-free,uniform or non-uniform icing conditions influenced only by ice mass or by mass and its stiffness together.And then they are comparatively modal analyzed to understand how ice mass and stiffness affect dynamic characteristics of the blade through MAC.The results show that ice can significantly increase the mass of blade resulting in reduced natural frequencies of blade,with the first-order flap-wise frequency decreasing by a maximum of 47.79 percent.At the same time,it can also increase the stiffness of blade resulting in the increase of the nature frequencies of blade,with the first-order torsional frequency increasing by a maximum of 39.51 percent.Flap-wise and lag-wise modal shapes of blade are less influenced by ice,but torsional modal shape of blade in 30 m^46.5 m is greatly affected among which it is the first torsional modal shape of blade under uniform icing condition that is influenced more obviously.