| It is a main constraint that poor starting performance of Straight-blade Vertical Axis Wind Turbine(SB-VAWT)at low wind speed and low wind energy utilization efficiency of hybrid wind turbine at high tip speed ratio to its development.In order to promote application of small vertical axis wind turbines in the field of small off-grid power generation and ensure easy-using in some areas such as pastoral area,island,country and so on,this paper is committed to design a modified Savonius rotor with elliptical blades and combined with SB-VAWT to improve power coefficient under the premise of wind turbine can start-up at low wind speed.In order to improve wind turbine performance,three main parameters are designed in the study include net overlap ratio of drag rotor,contour of drag rotor and relative angle between drag rotor and SB-VAWT.Numerical simulation and wind tunnel experiment are used conjunctively in this study.Firstly,net overlap ratio of drag rotor was simulation,according to the related literatures and some preliminary experimental results,5 net overlap ratios included 0,0.1,0.175,0.2,0.3 were simulated and the best result was elected.Then,contour of drag rotor was simulated under the premise of best net overlap ratio.9 parameters were set up from 0.8 to 1.6.After the two simulations,the parameters of drag rotor were determined.Finally,the drag rotor and SB-VAWT were combined at different angle(0°,30°,60°,90°,1200° and 150°)to explore the correlation between relative angle and hybrid wind turbine.In order to explore the effect of drag rotor to output power of VAWT,the Hybrid VAWT and SB-VAWT were simulated at 6 m/s,8 m/s and 10 m/s wind speeds in this paper.The flow field of wind turbine was also analyzed,at the same time the wind tunnel experiment was carried to test reliability about this simulation.In order to explore the effect of drag rotor to rotational speed character of SB-VAWT,the rotational speed of wind turbine with drag rotor or not were measured at 7 wind speed from 4 to 10 m/s and the effect of drag rotor on starting time and stable rotation speed of SB-VAWT was explored.Numerical simulation was combined to study the effect of drag rotor on static starting performance of SB-VAWT at 10 m/s wind speed and the flow field of wind turbine was analyzed,at the same time the wind tunnel experiment was carried to test reliability about this simulation.After the study on numerical simulation and wind tunnel experiment,some main conclusions can be obtained as follows:(1)The dynamic output characteristics and static starting performance could be effectively improved when the main structure parameters of drag rotor were reasonable changed.The better structure parameters of Hybrid VAWT in this paper as follows:the net overlap ratio is 0.2,the compression ratio of drag rotor is 1.4,the relative angle between drag rotor and SB-VAWT is 0.(2)The output power characteristics,stable rotation and starting performance of Hybrid VAWT with better structure parameters of drag rotor is better than SB-VAWT,and it could rotate at 4 m/s wind speed.(3)Hybrid VAWT with better structure parameters of drag rotor could obtain better starting performance,and the average static torque coefficient was improved 158.6%than SB-VAWT.In summary,this study verifies the validity for improve performance of hybrid wind turbine by reasonable changes the parameters of drag rotor and provides a new idea to change the parameters of drag rotor. |
PDF Full Text Request