Research On Wake Model Of H-type Vertical Axis Wind Turbine Based On Numerical Simulation

As the global become more and more concerned about the utilization of wind power, there are more and more researches about wind turbine, and wake performance is the key factor that should be understood. At present, most theories for wake are on horizontal axis wind turbine and they are already fairly improved, but the ones for vertical axis wind turbine are started to be paid more attention during these years due to the limit of its own factors. Considering the the big difference for aerodynamic performance between these two kinds of wind turbines, we can not design vertical axis wine turbine directly with the relative theories of horizontal axis wind turbine. For making the research for the vertical axis wine turbine deeper, this text will use Mathematical Simulation to research the wake of H-type vertical axis wind turbine.The major content includes:Study the aerodynamic performance of three common NACA airfoil types, simulate the process that flow on the surface of airfoil changes f rom attached-flow to separation-flow, and draw the curve showing the lift coefficient and lift-to-drag ratio change with the changes of the attack angel, the cloud diagram of wind speed at the back of airfoil and the distribution curve of velocity ratio there. Draw conclusions as following: the critical attack angel for these three types of airfoils are α=13°, the lift-to-drag ratio curves of these three types of airfoil are approximately parabola, lift coefficient and lift-to-drag ratio change more gently with the increasing of thickness of airfoil. The decreasing degree of speed of trailing edge of the same airfoil would increase with the increasing of attack angle, and symmetrica l distribution of trailing edge speed would disappear gradually with the increasing of inflow wind speed.Build the mathematical simulation model simplified mildly for two-dimension vertical axis wind turbine, and simulate rotation of wind turbine under d ifferent inflow wind speeds and different rotational speeds using Sliding Mesh. Calculate and analyze that at the same inflow wind speed, the airflow through wind rotor will decrease with the increasing of rotation speed, and the low velocity zone at the b ack of wind rotor will get larger and lager; at the same rotation speed, the center of low velocity zone inside the wind rotor will move to the back gradually with the increasing of inflow wind speed; analysis of the wind speed curve of rotor wake certifies the previous judgment about the changing regularity of low velocity zone, and meanwhile reveals the periodic variation regularity of wind speed outside the low velocity zone.Build separately mathematical simulation models of wind farm with two rows distribution and three rows distribution of wind turbine. Analyze speed curve between every row wind turbine and rotor power coefficient for every wind turbine in the wind farm. The result shows that, no matter which kind of distribution distance of wind turbine, the area within the distance of 3.5D from the rotation center of wind turbine is influenced more seriously by wake, while the velocity ratio outside the area increase according to the increasing of distribution distance of wind turbine; rotor power coefficient of the front wine turbine decreases due to the limit of wake development, the rotor power coefficient of the rear wine turbine decreases as well due to the influence of wake of front turbine; when the distribution distance reaches the critical distance, rotor power coefficient will stop increasing; this text finally draw a curve showing the rotor power coefficient change with the change of distribution distance, when design wind farm, consult this curve to determine the best distribution distance.