Investigation Into The Wake Velocity Field Of An H-Rotor Three-Bladed Vertical Axis Wind Turbine

As one of the important equipments for wind power generation,the vertical axis wind turbine has an important influence on the rational utilization of new energy sources and the sustainable development of society.Conventional horizontal axis wind turbines have poor safety performance,are not easy to install and maintain,and are difficult to apply to breeze generation.However,vertical axis wind turbine can effectively overcome these shortcomings.In recent years,the penetration rate of vertical axis wind turbine has been increased,and many scholars have devoted to studying the aerodynamic characteristics and the vibration excitation and response behavior under long-term operation.The effect of velocity distribution and wake effect on wind utilization is not studied.In order to supplement the above contents,this paper studies the wake velocity distribution of three-blade H-type vertical axis wind turbine by means of numerical simulation.Aiming at the single leaf of model NACA0018,the aerodynamic characteristics were obtained by means of numerical simulation.According to the extracted drag coefficient and pressure cloud,the stress analysis was carried out.The results showed that the critical attack angle was 8°.The lift and drag coefficient of the blade is positively correlated with the angle of attack,and the pressure on the upper and lower surfaces of the blade increases with the increase of the blade angle.By analyzing the velocity distribution curve at different distances from the trailing edge of the blade,the results show that the wind speed increases and the asymmetric degree of the velocity distribution curve of the blade increases.The angle of attack increases and the wake effect increases.With the increase of the distance from the trailing edge of the blade,it can effectively escape the effect of the wake effect and increase the recovery of the wake velocity.A vertical axis wind turbine model with three blades was established,and the feasibility of the simulation process was analyzed to ensure its accuracy.By changing the size of the wind speed and the blade speed ratio,the change of the wake velocity under the turbine cycle is discussed.The results show that the wind speed is increased and the low speed range of the rear of the turbine is expanded and the backward speed is increased.Recovery distance has increased.By increasing the velocity profile of the velocity curve from the different positions at the rear of the turbine,the increase of the turbine speed and the number of blades will increase the degree of asymmetry of the curve.In the transverse direction of the turbine,the flow effect is drastically attenuated.In addition,by studying the change of turbulence intensity,it is found that the overall variation is consistent with the wake velocity,but it is obviously slower than the recovery of wake velocity.Finally,the flow field structure of the turbine is given,and the specific area of the wake velocity attenuation,the influence range of the wake and the change of the turbulence intensity are divided,which provides the reference for the designers.Considering the complexity of the vertical velocity variation of the vertical axis wind turbine,taking the theory of wind farm as the background,the mutual interference effect of the two turbines is systematically studied.Based on CFD,two numerical simulation models of vertical axis wind turbines with the same specifications were established.The influence of wake effect on the power and wake velocity of adjacent two turbines was analyzed.The results show that the wind speed ratio increases with the increase of turbine spacing.But when the turbine longitudinal spacing of more than 9 times the diameter,the growth rate slowed down significantly.In this paper,comprehensive site and economic factors,this study will be a distance of 9 times the vertical diameter,horizontal 2 times the diameter of the two turbines as the preferred arrangement of the location.By changing the blade speed ratio,the wind power coefficient with the blade speed ratio of the law of change,the results show that with the blade speed ratio increased,the power coefficient increased firstly and then reduced,in this study under the conditions,when the blade speed ratio of 2,vertical axis wind turbine utilization is the best.