Research On Working Modal Test Of Small Wind Turbine Blade

Blade is the core components in small wind turbines,to optimize the structure of wind turbine blade layer design,with small wind turbine blade as the research object,the blade is larger,the influence of centrifugal force and dynamic force analysis by using on-board test blade working load,working load characteristics,through the effect on load simulation of stationary vane,reduction of work load,The experimental modal analysis was carried out to obtain the influence law of working load on modal parameters.It is of practical value to test the working mode of small wind turbine blades.Four sections of the blade are selected,which are 400 mm,500mm,800 mm and 1100 mm away from the rotation center in turn,and are defined as the first,second,third and fourth sections.The load test results show that: the rated wind speed is 8m/s,the second section has the maximum strain caused by the tension,the third section has the maximum tension of 468 N,and the middle part of the blade is the part with greater stress.The bending moment of the blade decreases from blade root to blade tip,and the first section near the blade root suffers the maximum bending moment,while the second section produces the maximum strain.In the range of 6～10m/s,with the increase of wind speed,the strain,tension and bending moment generated by different sections of the blade also increase.The modal test results show that the first order natural frequency and the second order natural frequency increase by 22.6% and 67.4% when the blade is under tension compared with the free state.The first and second order natural frequencies increase regularly with the increase of wind speed from 6m/s to 9m/s.The wind speed increases by 1m/s and 1～2Hz for each 1m/s increase.The bending moment has a significant effect on the first and second order natural frequencies of the blade,which is nearly twice that of the stationary blade.The variation of the first-order natural frequency when the tension and bending moment are simultaneously loaded is similar to that when the bending moment is loaded alone,and the variation of the second-order natural frequency is similar to that when the tension is loaded alone.The working load has little effect on the node position of the blade mode shape at the wind speed of 6～9m/s.