| In the modern society with energy shortage,wind energy,a kind of clean energy,quickly occupied the market.Under the influence of development of wind power market in recent years,the straight-bladed vertical axis wind turbine(SB-VAWT)had been widely concerned.However,as far as the current development results were concerned,the development of SB-VAWT was still restricted by some problems,such as the difficulty of self-starting at low wind speed and the low utilization coefficient of wind energy.This research explored the influence of part parameters of auxiliary blade on the output power of SB-VAWT,which was based on the auxiliary blade behind the SB-VAWT.It was expected to improve the wind energy utilization efficiency of SB-VAWT,which was under the premise of avoiding the complicated structure of wind turbine.In this study,the influence of the variation of the fixing angle and thickness of the auxiliary blade on the aerodynamic characteristics of SB-VAWT was studied,and it also built the foundation for the establishment of the parameters variation system of the auxiliary blade.In this study,2 types NACA-4 digital series symmetrical airfoils(NACA0018 airfoil and NACA0024 airfoil)were selected as the main blades,and 5 types NACA-4 digital series symmetrical airfoils with different thickness(NACA0012 airfoil,NACA0018 airfoil,NACA0022 airfoil,NACA0024 airfoil and NACA0026 airfoil)were selected as the auxiliary blade.And there were 3 kinds of fixing angles(0°,5° and 10°).A total of 13 working conditions were studied in this research.The numerical simulation method was used to analyze the effect of the parameters variation of auxiliary blade on the aerodynamic characteristics of SB-VAWT at low tip speed ratio.And wind tunnel test and PIV visualization test were carried out to verify the results.The main contents of this study are shown as follows:(1)The influence of the parameters variation of the auxiliary blade on dynamic aerodynamic characteristics of SB-VAWT was investigated,the numerical simulation method was used to calculate the influence of the parameters variation of the auxiliary on the output power characteristics and output torque characteristics of SB-VAWT.And the relatively optimal working conditions were selected for further analysis.And the wind tunnel tests were carried out to verify the calculations.(2)The influence of the auxiliary blade with different parameters on the flow field around the blades was analyzed.The working condition with the best performance in one rotating period was analyzed.The variation of the output power of the best working condition at the different azimuths in one rotating period was calculated.And the computational flow fields and the velocity distribution of the typical azimuth were analyzed.(3)The influence of the auxiliary blade with different parameters on the static starting characteristics of SB-VAWT.The variation of the starting torque of the optimal working condition at different azimuths in one rotating period was calculated by numerical simulation method.And the computational flow fields and the velocity distribution of the typical azimuth were analyzed.The PIV visualization test was conducted to verify the calculations.Through the analysis of the research contents,the conclusions are shown as below:(1)The auxiliary blade with variable parameters improved the aerodynamic characteristics of SB-VAWT.And it also improved the wind energy utilization coefficient of SB-VAWT to a certain extent.(2)In working condition A whose main blade airfoil is the NACA0018 airfoil,when the fixing angle is 0° and the auxiliary blade is NACA0012 airfoil,the output power is better than the working conditions with other thickness auxiliary blades.When the fixing angle is 5° and 10°,the overall output power of the auxiliary blade chosen NACA0018 airfoil which is medium thickness is best than the other working conditions.It can be seen from the calculation results that the overall output power of this working condition when the NACA0018 airfoil is the auxiliary blade and the fixing angle of auxiliary blade is 5° is higher than that of other working conditions in working condition A.It means that the output power of working condition A5 is the best in working condition A.(3)In working condition B whose main blade is the NACA0024 airfoil,the overall output power is the best at the low tip speed ratio when the NACA0022 airfoil is chosen as the auxiliary blade.It means that it is more advantageous that the thickness of auxiliary blade is close to than that of the main blade,not too thin or too thick.(4)The results of wind tunnel test are generally consistent with the results of numerical simulation.And the results of PIV test are basically consistent with the results of the flow field analysis The results of the tests prove that the auxiliary blade with variable parameters plays a positive role in improving the aerodynamic characteristics of SB-VAWTs. |
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