Aerodynamic Stability Analysis And Optimization Of Airfoil And Blade On Vertical Axis Wind Turbine

Vertical axis wind turbine(VAWT)has been being paid close attention since its concept has been born,as the most probable complementation of wind-electricity convertor to horizontal axis wind turbine(HAWT)to occupy the marketplace of wind energy.Researchers all over the world are conducting researches focusing on increasing wind power efficiency,which frequently result in increasing wind power efficiency one-sided while the operation stability and reliability being ignored.In this thesis,aerodynamic stability acts as an entry point of investigation on vertical axis wind turbine.A new set of airfoil and blade was supposed to be designed and adapted to the concept of stability.Main research work contains:Theory of aerodynamics of airfoil was brought in,including lift,drag,moment and aerodynamic center.Flat plate,NACA0012 and NACA23012 by velocity synthesis were computed under steady solver.Theory of turbulence was brought in,including turbulence kinetic energy,intensity,production,dissipation and viscosity.NACA0012,NACA2412 and NACA23012 by velocity synthesis were computed under steady solver.Results showed that NACA0012 had the most stable TKE and TI,the deviation of NACA0012 is largest with highest absolute value,and turbulence viscosity of NACA23012 is lowest;Idea of designing airfoil was come up with: chord line being identical to flight trajectory.Joukowski transformation and Trefftz Graphical Construction were combined to design new LJY series airfoil.New designed airfoil and other reference airfoils were put into curve wind tunnel computation domain to calculate turbulence.Results showed the designed airfoil behaved excellent,and TKE,TI,production,dissipation were lowest and turbulence viscosity highest in the computation of curve wind tunnel domain.Four popular blades' 3D configuration were compared: rectangular,elliptic,tapered,and sweepback,and computed by velocity synthesis under steady solver.Results showed proper modification of perpendicular blade can stabilize airflow and restrain turbulence to a large extent,although it did little about static forces and moment.Elliptic blade had been proved,both in theory and numerical simulation,to produce minimum induced drag.But it was observed to produce more turbulence in simulation.Tapered blade is taken example from the design of HAWT blade,and it was also responsible to the inhibition against turbulence.Although deviation of static moment upon sweepback blade was highest,the work to restrain turbulence was the most effective.New blade was designed by combining the advantage of sweepback and characteristic of flight trajectory.Mass and rotational inertia of turbine were calculated before using UDF and SDOF to build up the condition of fluid-driven simulation and observing the behavior of VAWT with airfoil NACA0012-800,LJY-800,NACA23012-800,and LJY-200.Results showed the potential of new designed airfoil and blade with better aerodynamic stability.Fluid-driven simulation gave out further suggestion that the traditional characteristic of high lift-drag coefficient and power coefficient may be impropriate for VAWT.Airfoil and blade design method adapted for VAWT in this thesis,as well as the perspective of aerodynamic stability to research on VAWT,is an essential reference to construct airfoil specially for VAWT with independent intellectual property of our country and popularization and application of VAWT.