Design And Evaluation Of Bionic Adaptive Wind Turbine Blade Based On Bending-twist Coupling Effect

Exploitation and development of wind energy, which is deemed as the green energy to replace resources of oil and coal depleting increasingly, is growing very fast in the world. Certainly, wind power technology has become the research hotspot recently. With the growing scale of wind turbine blade, a kind of blade possessing good flexibility and adaptivity will become the developing trend in the future. In this paper, the design and evaluation of adaptive blade based on bending-twist coupling is explored, combined with the bionic design from the flexible topological structure of plant tree leaf.The wind turbine blade is usually made of fiber composite material, whose performance can be enhanced through aero-elastic tailoring design. First of all, both of the analytic method based on the beam element theory and exemplification are used to verify the bending-twist coupling effect of composite blade, where the expressions of coupling efficient and blade stiffness are deduced also. After that, three models for coupling design are built refer to a 1.5MW blade as the baseline. Then, given the emphasis, the investigation of parametric design for off-axis fiber angle and fraction of coupled blade is conducted respectively. The results shows that, the glass/carbon hybrid fibers is the satisfactory material for coupling design, which can provide over 0.3 coupling coefficient between 15°~25°of off-axis fiber angle, rather than the all glass fiber. The peak tensile and compressive strain and stress increase obviously, except for the in-plane stress in hybrid fiber blades, with the off-axis fiber angle growing up. Notice that it should better to employ the fiber before 25°to ensure the blade structure safety. By comparison, the change of off-axis fiber fraction has less influence on the fiber strain and stress. From all sides, the blade with off-axis hybrid fibers cap should be considered as the optimal choice for coupling design.Integrating the coupling design, utilizing the flexible topological structure of palm tree leaf, a kind of bionic lay-up design method is developed, and is applied into the laminate design of coupled blade, proofing that can improve the blade bending-twist coupling effect further. The results also indicate the bionic adaptive blade has effect of load mitigation under critical wind loads. And the function of output power stabilization is reflected obviously in working wind speeds, especially beyond the rated speed. Even the wind speed is beyond the working speed within certain range, the wind turbine doesn't need to stop contribute to capture more annual wind energy hopefully. In addition, it is figured out the bionic coupled blade have a longer fatigue lifetime than all glass fiber baseline by Miner fatigue damage cumulative law.