Numerical Studies On The Aerodynamic Performance And Flow Control Of The Wind Turbines With The Magnus Effect

Against the background of wind energy has caught redoubled world-wide attentions, the technologies of wind power generation have been developed very rapidly in our country, and various new ideas to improve the aerodynamic performance of the wind turbine have been proposed incessantly. For the wind turbine, how to low the cost; improve the power efficiency; enhance the operational safety and reduce the impact on the environment and ecology are the problems confronted with all the researchers involved in this area. The introduction of the Magnus effect into the wind turbine blade to replace the ordinary wind turbine blade brings a new idea for the design and manufacture of the wind turbine. In this study, some results and conclusions have been obtained and are listed below:1,Concerning the characteristics of the wind turbine flow simulation, a low-speed preconditioning technique for the compressible Navier-Stokes equation has been developed.As the merits and drawbacks of the various numerical method for the wind turbine flow simulation are concerned, a preconditioning technique, which is based on pressure, velocity and enthalpy as the primitive variables to solve the compressible Reynolds-averaged Navier-Stokes equations under the rotational coordinate, has been developed in this work. The numerical method and the code have also been validated through several examples of 2-D airfoil flow. The results verified that the preconditioning technique can promote and accelerate the convergence of the low Mach number computations.Because there are still some difficulties in the multi-grid processing for the simulation of the 3-D wind turbine flow using the present code, the CFX software is used to do the following investigations of the wind turbine. 2,The numerical results of our studies have been validated through several examplesThe numerical simulations of the 2-D steady NACA 63418 airfoil flow and the 2-D unsteady stationary circular cylinder flow and the 3-D steady NREL Phaseâ…¥wind turbine flow have been conducted and then validated through the comparisons with the corresponding experimental results. The results show that, for the attached flow before the stall, the computed results agree well with the measured datum; while for the separated flow under the stall condition, the computed results become less accurate, but still comparable.3,The numerical studies on the aerodynamic performances and flow controls of the Magnus wind turbines equipped with several circular cylinders of various aspect ratios, circular cones and wavy cylinders of various wave lengths as the blade have been conducted respectively.The results show that, the tip speed ratio of the rotor and the rotational speed ratio of the cylinder are the two important dimensionless parameters of the Magnus wind turbines. The power coefficient of the Magnus wind turbine first increases then decreases with the increasing tip speed ratio and rotational speed ratio, and the thrust coefficient increases with the increasing tip speed ratio and rotational speed ratio. The power output and the thrust load of the Magnus wind turbine can be well controlled through the rotating circular cylinders.For the Magnus turbine equipped with circular cylinders, the range of the normal-operational tip speed ratios and the maximum power coefficient are determined through the aspect ratio of the cylinder. For the Magnus wind turbine equipped with circular cones, if the tip speed ratio and rotational speed ratio is low, because of the loss of the local rotational speed ratio on the inboard of the blade, its power coefficient is also relatively low compared with the Magnus wind turbine equipped with circular cylinders; while if the tip speed ratio and rotational speed ratio is high, the maximum power coefficient is improved manifestly. For the Magnus wind turbine equipped with wavy cylinders, since the aerodynamic force of the rotating wavy cylinder is not satisfying, the power consumptions of the rotating blades are too high, so its power coefficient is relatively low.4,A new type of wind turbine with leading edge rotation have been conceived and the numerical studies on the aerodynamic performances and flow controls of the wind turbine with leading edge rotation have been conducted.The designs of the geometrical control parameters of the NACA 63418 airfoil with leading edge rotation have been conducted through numerical computations, and the clearance width and the size of the rotating cylinder at the leading edge of the controlled NACA 63418 airfoil have been obtained.Firstly, the numerical studies on the aerodynamic performances of the NACA 63418 airfoil with leading edge rotation have been conducted. The results show that, if the angle of attack is small, due to the flow separation on the pressure side of the airfoil near the clearance, the control effect of the leading edge rotating cylinder is not satisfying; if the angle of attack is large, the flow separation on the suction side of the airfoil can be suppressed efficiently through the leading edge rotating cylinder, the stall of the airfoil is delayed and the aerodynamic performance of the airfoil is improved dramatically.On the basis of the 2-D investigations, the aerodynamic performances of the 3-D wind turbine rotors with leading edge rotation have been studied. The results show that, the aerodynamic performance of the non-tapered wind turbine with leading-edge rotation is remarkably superior to that of the tapered wind turbine with leading-edge rotation. The comparisons of the pressure distribution on the blade have been made and the results show that especially at high tip speed ratios, there is an enhanced low pressure peak on the suction side of the rotating cylinder, so the power efficiency of the wind turbine is improved. The studies on the pitch angles of the blade suggest that, the angle of attack of the blade should not be too large to ensure the flow control effect of the leading edge rotation on the wind turbine.In addition, the aerodynamic control abilities of the leading edge rotating cylinder on the non-tapered wind turbine have been studied, and therefore an aerodynamic control method under various wind speeds has been proposed, which can improve power output from wind turbines by adjusting the cylinder rotational speed.