Research On The Optimization And Aerodynamic Characteristics Of The Blunt Trailing Edge Airfoil Of The Frost Horizontal Axis Wind Turbine Blade

Horizontal axis wind turbines mostly work in cold,coastal and other harsh environments,often encounter extreme weather such as rain and snow.At this time,ice will appear on the surface of the blades.Icing changes aerodynamic shape of the blade and increases the surface roughness,which reduces the lift coefficient and increases the drag coefficient,resulting a decrease in output power.In view of the limitations of external treatment methods,optimum design to reduce the impact of icing on the blades’aerodynamic performance has become a hot spot in the research of wind turbine blade surface anti-icing.In the present study,a multi-objective optimization method for blunt trailing-edge airfoil with rough surface is proposed,taking the maximum lift coeff-icient and lift-drag ratio as the optimization objective.Applying the idea of mathematical dimension reduction,a new method(BRISF)for obtaining rime ice shape on blade surface by fitting ice shape of multi-section along the blade spreading direction is proposed.The blunt trailing-edge of airfoil is optimized under rime ice conditions.Then the blunt trailing-edge blade with rime ice shape is obtained by BRISF method,and its output power and flow field characteristics are studied.The main research work and achievements are as follows:(1)By using airfoil profile integration theory and B-spline curve,the parametric expressions of blunt trailing-edge airfoil profile are established.The convex platform is used to simulate the roughness,and the particle swarm optimization(PSO)coupled with XFOIL software is used to optimize the multi-objective design of blunt trailing-edge airfoil with rough surfaces.The flow field characteristics,aerodynamic performance and roughness sensitivity of the airfoil before and after optimization are calculated.The results show that the optimized surface rough blunt trailing-edge airfoil has low roughness sensitivity.The blunt trailing-edge can block the suction surface airflow,improve the pressure distribution on the airfoil surface,and improve the aerodynamic performance significantly.(2)For three different step size ways,the linear interpolation method is used to fit the airfoil’s ice shape,and the airfoil’s rime ice shape formation method(LIEEAS)is proposed.Based on this method and the idea of dimension reduction,the coordinates of the key points of icing shape along the blade span are mapped into the flaping and lagging planes respectively,and the rime ice shape of the blade is obtained by polynomial fitting.The reliability of the LIIESA and BRISF methods is qualitatively and quantitatively studied separately.The results show that the ice shape obtained by BRISF method is basically the same as that obtained by FENSAP numerical simulation.The sum of total residual squares of LIEEAS and experimental results,BRISF and FENSAP results are small,and the order of magnitucde is only 10-4 or 10-5.(3)Combining with the LIEEAS method and using particle swarm optimization coupled with GAMBIT and FLUENT software,the optimization design of blunt trailing-edge airfoil under rime ice conditions is carried out.The aerodynamic performance and flow field characteristics of the airfoil before and after optimization are compared and studied.The results show that when the rime ice blunt trailing-edge airfoil is optimized,the lift coefficient increases and the stall delay is delayed,the differential pressure between the upper and lower airfoils increases,and the aerodynamic performance is significantly improved.(4)Based on the optimized blunt trailing-edge airfoil under rime ice conditions,the rime ice blunt trailing-edge blade is established by using BRISF method.Torque,output power and flow field characteristics of clean blade and rime ice tip,blunt trailing-edge blade are compared and analyzed.The results show that the Ooutput power and aerodynamic performance of rime ice tip trailing-edge blades are lower than those of clearn blades.The output puower and aerodynamic performance of rime ice blunt trailing-edge blade are better than that of rime ice tip trailing-edge blade.