Study On Flow,Load And Noise Characteristics Of Deformable Trailing Edge Flap Based On Fluid-Structure Coupling Model

Currently,the large-scale technology development trend of wind turbines has led to the continuous increase of blade size and structural flexibility.In actual operation,the fatigue load and extreme load problems of wind turbines caused by turbulence,wind shear and tower shadow effects are becoming more and more serious,significantly reducing the structural safety and reliability of wind turbines.As the most promising active control technology,Deformable trailing edge flap(DTEF)can effectively reduce the blade load level and further reduce the load level of other components of the unit,such as the hub,tower and transmission system,thereby improving the reliability of the unit.After fully understanding the current research status of blade load control technology at home and abroad,this paper has completed the research summary of the trailing edge flap intelligent blade load control technology.On this basis,a n aeroservo-elastic platform for the large-scale wind turbine,CFD/Open FAST,is built based on the fluid-structure coupling method and is embedded with the DTEF control module.And the active control over flow,load and noise of the DTEF for wind turbine have been systematically studied.The main tasks completed by the thesis include:1)An aero-servo-elastic platform for the large-scale wind turbine,CFD/Open FAST,has been built.In the construction of the computing platform,a multi-stage motion transmission mechanism of "large range-medium range-small range" was established for the motion transfer process.For the load transfer process,based on the established "F-N" pairing relationship,applying the fluid boundary surface to the onedimensional beam node,the aerodynamic load is transferred from three-dimensional to one-dimensional mapping.For the time advancement of the coupled platform,the "asynchronous/internal iterative step" combination mechanism is adopted to ensure the stable convergence of the coupled architecture.The comparative verification results based on Phase Ⅵ wind turbine wind tunnel test prove the reliability of the CFD/Open FAST simulation computing platform.2)The flow control mechanism and characteristics of DTEF has been clarified.The research results show that the flow control mechanism of the DTEF is mainly reflected in the swing of the Deformable trailing edge,so that the effective camber of the airfoil can be adjusted in a timely manner,which significantly changes the pressure distribution on the airfoil surface and affects the airflow.This kind of Deformable swing brings a significant improvement in the aerodynamic performance of the airfoil.For example,while increasing the periodic average lift,it reduces the maximum lift and stabilizes the aerodynamic output.In addition,this paper also deeply discussed the influence of different DTEF design parameters on the aerodynamic performance of the two-dimensional airfoil.3)The local load control of the DTEF for the wind turbine blade under unsteady flow is studied.The results of variable wind speed studies show that the maximum deflection speed and maximum deflection angle of the DTEF significantly affect its control efficiency,that is,lower control parameters will limit the control of the DTEF over the blade load.However,after the control parameter reaches a cert ain level,continuing to increase the parameter cannot improve the load control efficiency of the DTEF.The results of the variable wind direction studies show that the DTEF can effectively resist short-period small-amplitude changes in wind direction The blade load is unstable,but with the significant increase in the amplitude of the wind direction change,the control ability of the DTEF is significantly reduced.4)The active control characteristics of the DTEF on the fatigue and extreme load of the blade and the tower under the IEC/GL standard wind conditions are further studied.Taking the NREL 5MW reference wind turbine with DTEFs as the research object,the fluid-structure coupling numerical analysis model of wind turbines was established by CFD/Open FAST.After model verification,fatigue load control research of the DTEF under NWP wind condition were completed,in which the work of DTEF significantly reduces the load and displacement response of blades and towers,but has a slight impact on the output of wind turbines.Research on the ultimate load control of the wind turbines of the DTEF under EOG wind conditions have been completed,in which trailing edge flaps,through the adjustment mechanism of “reducing peaks-raising valleys”,significantly improves the extreme improves the extreme load impact on the blades and towers of wind turbines under extreme working conditions.5)The influence of the DTEF on the aerodynamic noise of the blade is analyzed.The research results show that while the DTEF adjusts the aerodynamic performance of the airfoil,it does not significantly change the aerodynamic noise of the increased airfoil.In the research on the effect of flexible trailing edge gap on blade aerodynamic noise,the effect of the truncated length of the trailing edge on the aerodynamic and noise characteristics is discussed.The results show that increasing the trailing edge truncated length will reduce the aerodynamic performance of the airfoil and has a tendency to deteriorate its performance.Airfoil aerodynamic noise also shows a similar increase,and with the increase of the truncated length of the trailing edge,the main frequency of the noise keeps decreasing and the peak value keeps increasing.