| Currently, the promotion and application of small and medium-sized wind power industry is derived by large-scaled one. Thence, research and development of small and medium-sized wind power system, which is suitable for off-grid and distributed use, is taken seriously. Among which, Straight-Wing Vertical Axis Wind Turbine(SW-VAWT) is widely concerned by its advantages of simple structure, favorable wind adaptability, convenience installation and maintenance. However, some drawbacks of the wind turbine can be discovered by researches, such as that poor starting performance at low wind speed and low wind energy utilization efficiency, which is compared with Horizontal Axis Wind Turbine.In order to improve the starting performance under low wind speed and wind energy utilization efficiency, a new type Vertical Axis Wind Turbine with double-layer retractile blades is designed in the study. The wind turbine is an L-resistance composite one based on current straightwing vertical axis wind turbine. The wind turbine blade includes outer and inner blade, the outer layer is primary blade that provides main rotating torque, and the inner layer is secondary one, whose purpose is to install flexible auxiliary blades elastic at its maximum thickness, which will offer rotating torque at start time and assist torque at normal operation. When the wind turbine is active, low rotor speed, flexible auxiliary blade will open, and then resistant wind wheel is constituted, then produce greater torque, the wind turbine as a whole can quickly start to solve linear vertical axis wind wing machine startup problems. When the wind wheel starts, flexible auxiliary blade retracted deputy blades, lift characteristics of wind turbine recovered, the rotation of wind turbine blades mainly relied on the torque generated by the rotating outer, inner blade plays a supporting role to wind turbine rotation, which can improve the utilization of wind energy to some extent. This wind turbine of the structure has not been reported yet. In this paper, research of the main structural parameters of Vertical Axis Wind Turbine with double-layer retractile blades designed in the study by numerical methods firstly, which include the installation location of inner blade, the spread outline of flexible auxiliary blade etc. Then under the best structural parameters carried the wind tunnel experiment by the experimental model, the reliability of the calculation results was test. At last, the main structure of this kind wind turbine is designed. Main calculation results are summarized as follows:(1)The installation position along the radius direction of the blade has great influence on the aerodynamic characteristics of wind machine. The results show that the double-layer blade can enhance the moment coefficient of wind turbine effectively, and improve wind energy utilization of wind turbine. In addition to this, the install location of inner blade along radial direction has a greater impact on torque characteristics and power. The effect is best while radius ratio is 0.7.(2)Relative installation angle has smaller influence on aerodynamic characteristics of wind turbines. Under the radius ratio of 0.7, choose the relative installation angle from-45 degree to 45 and the results show that the wind turbines torque characteristics under different relative installation angle has no obvious difference between the power characteristic(3)In the calculation of the optimal curve flexible auxiliary blade, comparing with aerodynamic characteristics of Savonius rotor, seven different compression ratio of the elliptic curves were calculated and analyzed, and results shows that at low tip speed ratio wind turbine has good torque characteristics when the elliptical compression ratio is 1.6 of the elliptic curve as an outline, then the start of wind turbine can be achieved.In calculating optimal curve of flexible auxiliary blade, the traditional analogy Savonius wind turbine aerodynamic characteristics, to seven different compression ratio of the elliptic curve to carry on the calculation and analysis, the results show that the elliptical compression ratio is 1.6 of the elliptic curve is an outline, in lower tip speed ratio wind machine has better torque characteristic, can complete since the launch of wind turbine.In summary, this study has two main innovations: Firstly, a new type of lift and drag composite vertical axis wind turbine was designed, and related structures were also designed to solve the poor startup problems of traditional straight-wing vertical axis wind turbine, simultaneously, wind energy utilization was improved; Secondly, the main structural parameters of the wind turbine were studied using numerical methods, then influence of parameters on aerodynamic performance of wind turbine was obtained. These results will offer theoretical basis and reference for the further research and apply. |
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