Investigation On Aerodynamic Performance Of Horizontal Axis Wind Turbine By Setting Micro-cylinder In Front Of The Blade Leading Edge

Focusing on the characteristics of flow separation for HAWT operating under large flow conditions,this paper studies a controlling method by adding a micro-cylinder in front of blade leading edge for NREL Phase VI wind turbine.The corresponding numerical simulation analysis for this new type of HAWT and the aerodynamic characteristics of flow field are analyzed.The main contents and achievements of this paper are showed as following:Firstly,the results predicted by simulation are confirmed with experimental results.Under the same operating conditions,the simulation and experimental results of torque and bending moment are compared,as well as results from other studies.It can be found that the simulation results can accurately reflect the basic physical characteristics of flow field for NREL Phase VI wind turbine.Secondly,the influence of different diameters and positions of micro-cylinders on aerodynamic performance of wind turbine is discussed.Numerical results suggest that under different stall conditions,setting appropriate micro-cylinders in front of blade leading edge can effectively suppress the flow separation on wind turbine blades with increasing the load of wind turbine slightly.Moreover,under different wind speeds,micro-cylinders with different diameters and positions have various impacts on aerodynamic performance of wind turbine.Thirdly,the concept of relative inflow angle is introduced.The control mechanism of micro-cylinders with different positions on reducing the flow separation of the horizontal axis wind turbine blade is studied.Under the condition of U_?=13m/s,when it is closer to the blade tip,the relative inflow angle decreases gradually and tends to a stable range.The optimum micro-cylinder on each cross section gradually approaches to the blade leading edge with the decrease of relative inflow angle.The optimal effect cannot be achieved when using the integrated micro-cylinder formed from the optimal micro-cylinder segments on each cross section.The flow field at the cross sections could be influenced by the upper and lower parts due to its complexity.In addition,according to the actual situation of fluid solid coupling simulation,two kinds of micro-cylinder vibration modes are set up,and the aerodynamic performance is numerically investigated.The influence of vibration modes,amplitude and frequency on the aerodynamic performance of horizontal axis wind turbine is explored.Numerical results suggest that in the case of different stall conditions,setting appropriate vibration micro-cylinder can effectively suppress the flow separation on wind turbine blades than installing static one.Besides,the vibration micro-cylinder also shows obvious suppressing effect on large flow separation.When U_??13m/s,the vibration direction and amplitude play a leading role in the improvement of aerodynamic performance,and a micro-cylinder with high vibration frequency can suppress surface flow separation more quickly to achieve the optimum aerodynamic performance.Based on calculation,when U_?=10~25m/s,by setting micro-cylinders which are close to the blade surface with suitable vibration rules,the wind energy coefficient can show an increase of86.2%,188.4%,214.1%,109.8%and 120.2%,respectively,compared with those of adding static micro-cylinder or without adding micro-cylinder.