Research On Aerodynamic Characteristics Of Savonius Wind Turbine With A Folding Guide Vane

The Savonius wind turbine has the advantages of simple structure,less susceptible to wind direction,better starting performance compared to other wind turbines.However,the low utilization of wind energy has become the main reason for limiting its development.At the same time,under certain azimuth angles,the static torque coefficient is low,which also affects the starting characteristics of the wind turbine.In order to improve the output power performance and static starting torque characteristics of Savonius wind turbines,this study designed a folding guide vane which can be installed on the outside of the Savonius rotor to geather inflow more efficiency,improve the flow field around the rotor and the overall performance of the wind turbine.Numerical calculations and wind tunnel tests were carried out on the three main structural parameters of the folding guide vane,including the number of guide vane,the distance between the guide vane and the wind turbine,and the angle between the guide vane and the inflow.In addition,before the study of the guide vane,the overlap ratio of Savonius wind turbines was first analyzed,and the static starting torque of Savonius wind turbines with three typical overlap ratios by means of numerical simulation were carried out which were used to compared the PIV visualization test results.The main research content is as follows:(1)Three overlapping ratios were selected: 0,0.2,and 0.5,numerical simulations were carried out on the static starting torque with three overlapping ratio Savonius wind turbines.The flow field around the rotor at 35°,90° and 165° azimuth angles was measured by the PIV visualization test and compared with the numerical simulations results.(2)A folding guide vane was designed.Three main parameters were defined,namely the number of guide vane,the distance between the guide vane and the wind turbine,and the angle between the guide vane and the incoming flow.By using the orthogonal design method,9 combinations of parameter configuration schemes were obtained.The maximum average static torque coefficient was used as the object.The static torque of the wind turbine was studied by using numerical calculation method.A group of better structure parameters of the guide vane was obtained.The wind tunnel test was carried out to compare with the numerical simulations results.(3)The output power characteristics of the Savonius wind turbine at three wind speeds were studied by comparing the results of numerical simulation and wind tunnel test of the Savonius wind turbine with the obtained optimal structure parameters of the guide vane.The dynamic torque characteristics in one rotation cycle were also calculated,and the flow around the rotor was analyzed.Through the above studies,the main conclusions obtained under the conditions of this study are as follows:(1)The overlap ratio had a significant effect on the static torque of the Savonius wind turbine.When the relative overlap ratio is 0 and 0.5,the wind turbine has a better torque coefficient when the overlap ratio is 0.2.Through the analysis and calculation of the flow field obtained by the experiment,it was found that the existence of overlap ratio can effectively eliminate the vortex inside the wind turbine rotor,reduce energy consumption,and increase the torque coefficient.(2)The folding guide vane can improve the static torque characteristics of the Savonius wind turbine.At most azimuth angles,the guide vane improved the inflow of the wind turbine at rest.A group of better deflector parameters were obtained: the number of guide vane was 4,the angle between the guide vane and the incoming flow was 15°,the distance between the guide vane and the wind turbine was 46 mm,and the average static distance-coefficient was 45.9% higher than original Savonius wind turbine.(3)For the output power characteristics,the Savonius wind turbine with better guide vane parameters had higher wind energy utilization than the original wind turbine,and the improvement effect was more significant with the increase of wind speed.The guide vane could also improve the dynamic flow around the wind turbine rotor,and the dynamic torque in most azimuths was also increased.The results obtained in this study can provide reference for the overall improvement of Savonius wind turbine performance,and provide new ideas for the research of Savonius wind turbines.