Wind Turtnel Test Research On Wake Interaction Characteristics Of Wind Turbines

In recent years,wind farms have gradually developed in the direction of large-scale clusters,and the wake effects of wind turbines have also received more anf more attention.The wake effect of the upstream wind turbine will decrease the output power of the downstream wind turbine,in a large wind farm,the power loss caused by the wake effect can reach 10%-20%of the annual power generation.In addition,the intensity of turbulence in the wake of the wind turbine is relatively large,when the wind turbine is in a high turbulence area for a long time,it will increase the fatigue load of the blades and the tower,thereby shortening its service life.Therefore,research on the wake structure of wind turbines and their mutual interference is of great significance to the flow field analysis of wind turbines and the rational optimization of the layout of wind turbines.In order to explore the wake interaction characteristics of multiple wind turbines and provide a basis for establishing a high-precision wake model,the author used the wind tunnel test method to carry out the wake field structure test of a single wind turbine and two wind turbines under 10 working conditions such as the head-on wind,yaw,and stagger.The experimental platform was built in a large low-speed return wind tunnel with a cross-section of 3m×3m and a length of 20m.Two wind turbine models were designed and customized,and a hot-wire anemometer was used as a flow field measurement instrument.The main research content is:(1)Wind tunnel test study on wake characteristics of a single wind turbine.In the case of a given incoming wind speed as 8m/s,under the head-on wind and yaw conditions,use the hot wire anemometer to measure the wake field within 1-7D(D is the diameter of the wind rotor)behind a single wind turbine to obtain the message of the distribution of velocity and turbulence intensity in the field.The results show that:at about 3D from the front of the wind turbine,the incoming wind speed will drop significantly.The wake attenuation coefficient is positively correlated with the yaw angle.At a low tip speed ratio(λ=1.8),when no yaw occurs,the wake attenuation coefficient is 0.032;when the yaw angle is 10°,the wake attenuation coefficient is 0.036;When the yaw angle is 20°,the wake attenuation coefficient increases to 0.043.Yaw can effectively reduce the speed loss of the incoming wind speed,and there is an asymmetry in the speed profile under yaw conditions.(2)Wind tunnel test study on wake interaction characteristics of two wind turbines.In the case of a given incoming wind speed as 8m/s,under the conditions of head-on wind,stagger,yaw,use the hot wire anemometer to measure the wake field within 1-7D behind the two wind turbines to obtain the velocity in the flow field and the distribution of turbulence intensity.The results show that:under the head-on wind condition,the wake of the upstream wind turbine will interfere with the wake of the downstream wind turbine,which will aggravate the wake loss of the downstream wind turbine;staggering can effectively reduce the impact of the wake of the upstream wind turbine,and the wake of the downstream wind turbine has a tendency to deviate in the negative direction(the opposite direction of the yaw);under yaw conditions,the speed loss of the upstream and downstream wind turbines is the smallest when they yaw in the same direction.It has been verified that the superposition model is only applicable to head-on wind condition,and the sum of square superposition model has the best effect.The experimental data and characteristics of the wake field of a single wind turbine and the interaction flow field of two wind turbines obtained from the above-mentioned experimental research,it can provide important data and physical mechanism support for the development and verification of high-precision wake models of wind turbines.