Simulation And Experimental Research On Trailing Edge Flap Smart Load Control System Of Large Wind Turbine Blade

With the development of large-scale wind turbines,trailing edge flap,one of the smart blade load control methods,can effectively,quickly,and flexibly reduce wind turbines,especially large wind turbines blade fatigue load.For its effectiveness and economy,the flap control method had received widespread attention at home and abroad.To further understand the actual effect of blade flaps and the load reduction mechanism,based on horizontal model wind turbines with trailing edge flap control,wind turbine performance simulation,wind tunnel experiments,and blade flow field CFD research work were carried out.Flap control system scheme,performance calculation,and model horizontal wind turbine experimental verification constructed the whole research system.Firstly,based on the independent research for aerodynamic-servo-elastic coupling simulation calculation platform of large wind turbine with flexible tail flap control,under the different wind speeds,the effectiveness of the tail edge flap load intelligent control system is demonstrated from the performance of the whole wind turbine.The blade characteristic parameters distribution under different azimuths were carried out.It is determined that the intelligent control system of the trailing edge flaps can effectively suppress the fluctuations of the motor output power,thrust,and pitch angle without affecting the output of the wind turbine generating capacity.According to research the coupling relationship between the blade aerodynamic load and the blade movement,the reason why the trailing edge flap can effectively suppress the fatigue load of the blade is summarized.To further the calculation results and improve the research system,based on completing the performance calculation of the prototype wind turbine,a new experimental study of the model wind turbine with the active control of the trailing edge flap was carried out.An open wind tunnel for model horizontal axis wind turbine test system was built,and blades with independently designed flap actuation systems were installed.Wind tunnel experiments under different operating conditions and flap control strategies were carried out.For the size limitation of the wind tunnel in the lab,experimental wind turbine blades,for the model of NREL 5MW wind turbine,were designed according to the size at a ratio of 1:105.In addition to meeting the requirements of the similar law,and ensure the similar aeroelastic characteristics of the blades,the blade Polar line spanwise distribution was introduced.A servo motor is used to drive the flaps,and the aerodynamic shape design of the model blade is optimized according to the BEM theory.A horizontal axis model wind turbine experimental test system was built and carried out the experimental research on the performance of the flap active control fatigue load system.The system consists of an open wind tunnel,a horizontal axis model wind turbine with a trailing edge flap actuation system,a motor control system,and a measurement system.In the beginning,an experimental study was conducted under the wind turbine stopped status,and the goal of the experiment was to investigate the changes in the flow field around the blade with flap swinging.According to the wind tunnel experiment in the shutdown state,CFD calculation was carried out,which can capture the details of blade flow field changes and can describe the flow field change process.It is also possible to study the changes in flow field characteristics under different incoming wind conditions and flap control strategies.In the end,the process of the influence of flap swing on the aerodynamic load of the blade under the condition of uniform flow is summarized.Combining the analysis of the aeroelastic coupling characteristics of large-scale wind turbine blades,wind tunnel experiments,and numerical calculations,the mechanism of the active control system of the trailing edge flap to suppress the fatigue load of wind turbine blades is systematically described.Finally,the trailing edge flap load control experiment of the horizontal axis wind turbine under the rotating state was carried out.Under the conditions of uniform flow,three flap open-loop control strategies were formulated: the flap swings to the amplitude position to hold,the flap sine wave signal control,and the flap square wave signal control.By comparing the experimental results and the performance costs of different control signals,the open-loop control method with the most obvious control effect on the deformation of the blade root is finally determined.Using an open-loop control strategy with an obvious load suppression effect,a comparative experiment between the yaw state and the direct blow state was carried out to explore the effect of the flaps in the yaw state.The experimental results show that the same flap open-loop control strategy can achieve better load control effects in the yaw state than in the direct blow state.It shows that for real wind conditions,which are more complicated and variable using the trailing edge flap smart control system to control the blade fatigue load of large wind turbines will have greater application capacities.With the help of NREL FAST aero-servo-elastic performance simulation,CFD numerical calculation,model wind turbine open wind tunnel experiment and other research methods,the role of the trailing edge flap smart control system in suppressing the fatigue load of large wind turbine blades were explored,and the flap fatigue load control mechanism was fully revealed The blade load control mechanism provides an effective reference for the engineering application of the trailing edge flap smart control system in the large-size wind turbine.