Numerical Simulation Of Aerodynamic Performance For Horizontal Axis Wind Turbine

At present, the renewable energy attracts people's more attentions as the environment is becoming worse and supply of energy is getting tenser. As one type of renewable electricity-generation, wind power is not only clean but also more mature in technology and able to be explored in larger scale compared with other types of renewable energy. Therefore, it is being acclaimed and emphasized by most nations. However, There are lots of problems to be solved concerning about wind power, of which aerodynamic performance is the basic one. To study the aerodynamic performance, mostly widely applied is blade element momentum theory, which is based on several hypothesis that lead to imprecisely predicting aerodynamic performance of wind turbine. But now, with the development of modern computer technology and simulation method of 3D turbulence, CFD is playing more significant roles in studying aerodynamic performance. Based on this, the representative wind turbine S809 airfoil and PhaseⅥrotor were selected as the research objects in the paper and the steady flows around them were simulated.Firstly,both 2D and 3D physical, mathematical models of the flows around the airfoil were built, and the turbulence was treated separately by using Spalart-Allmaras model and k-ωSST model. Then the models were solved numerically. The computational domains were discretized by employing structured quadrilateral or hexahedron meshes, and the turbulence near the wall was treated by applying enhanced wall function method. In the process of computation, the coupled computation of pressure and velocity variable was completed with the SIMPLE algorithm. The computed angles of attack ranged from 1°to 20°and Reynold number and Mach number of incoming flow were set to be 1×106 and 0.07333. Computed results are compared with experimental data from DTU, based on which the boundary separated flows were analyzed and the conclusion can be drawn that the computed results form the 3D and Spalart-Allmaras turbulence model were more accurate.Then 3D physical and mathematical models of the flow around rotational blade were built in the rotational coordinate system based on the blade, and turbulence was computed by using Spalart-Allmaras model which had been proved to be more accurate in computing the aerodynamic performance of the airfoil. Likewise, the models were solved numerically. In the process of building physical model, based on limited blade data spatial coordinates were produced in EXCEL which were input to Gambit and 3D geometric model of the PhaseⅥblade was obtained. In the course of computation, the pressure was discretized by employing the PRESTO scheme which was more valid in treating the rotational flow with highly pressure gradient and other variables were discretized with second order upwind scheme. Multi-step solving and sub-relaxation techniques were applied here to benefit the converging of solutionsThe aerodynamic performance of PhaseⅥrotor was simulated numerically under the UAE conditions, based on which the shaft torque, rotor power coefficient and the normal force coefficients at several radial locations were analyzed. Then they were compared with experimental data from UAE. Meanwhile, the 3D rotation effect on aerodynamic performance of the airfoil was discussed as well. Based on the above, the impacts of the pitch angle and rotation speed on the rotor performance were studied which would lay foundations for further research.