螺旋型垂直轴风力机的气动性能研究及结构参数优化

在H型垂直轴风力机的研究基础上,针对其启动性能较差、风能利用系数低等问题,提出了一种螺旋型垂直轴风轮。首先基于流管模型通过MATLAB编程对其性能开展了粗略分析,然后通过Fluent软件对螺旋型风轮进行了数值模拟,研究了风轮结构参数对其气动性能和启动性能的影响规律,并将优化的螺旋型风轮与同扫掠面积的H型风轮进行了对比。结果表明螺旋型风轮在旋转一周过程中,力矩系数波动幅度不超过40%,且力矩系数均为正值,利于其启动;此外,螺旋型风轮的风能利用系数也较H型风轮高2%~3%,尤其是在叶尖速比较低的情况。该文提出的螺旋型风力机较之H型风力机,在旋转过程中力矩系数变化小,在4 m/s风速即可启动,拓宽了可利用的风能范围,在低风速区域更适用,且整体风能利用系数也能有所提升。

Aerodynamic performance research and structural parameter optimization of helical vertical axis wind turbine

Abstract: Vertical axis wind turbine (VAWT) has the advantages of good adaptability to wind direction, low noise, simple structure, and so on. It has a good application value in the field of small and medium-sized wind turbines. Among all kinds of VAWTs, H type VAWT is used more widely and has better performance. However, it still has some drawbacks, such as poor starting performance, low utilization coefficient of wind energy, large torque fluctuation in the process of rotation, alternating load and fatigue of the wind wheel. In this paper, a scheme for forming a helical VAWT by rotating a straight blade of an H type wind turbine to a certain angle is presented. The performance analysis and parameter optimization of this kind of wind turbine are carried out. First of all, the working principle and force situation of the helical wind turbine are analyzed, and a rough analysis of its performance is carried out based on the flow pipe model through MATLAB programming. In this process, the influence law of blade rotation angle on tangential force coefficient of wind turbine is studied. Hence, a preliminary physical model of helical wind turbine is obtained, which is a rotor consisting of 3 blades with 120° rotation. Then, the helical wind turbine is simulated by Fluent software. In the process of numerical simulation, we choose the torque coefficient as the validation parameter to carry out the grid independent verification analysis at first. Secondly, the influence of wind speed on the aerodynamic performance of wind turbine is studied. Thirdly, the effects of a few key parameters on the wind turbine''s aerodynamic performance and starting performance are researched. They are blade number, chord length, and ratio of height to diameter of the wind turbine. With the power coefficient as the evaluation index, the power coefficient of the wind turbine at different tip speed ratio is calculated by changing a parameter value of the wind turbine every time. Consequently, a set of optimized wind turbine structural parameters are obtained: Blade number is 3, chord length is 320 mm, and ratio of height to diameter is 1.8. At last, the wind energy utilization coefficients and torque coefficients of the optimized helical type wind turbine and an H type wind turbine with the same swept area are calculated by Fluent software, and the results are compared and analyzed. The results show that the torque coefficient of the helical wheel fluctuates less than 40% during its one-week rotation, and the torque coefficient is always positive, which is beneficial to start up. The torque coefficient of the H type wind turbine is negative at the azimuthal angle of 0 and 180°, showing poor starting performance. In addition, the overall coefficient of wind energy utilization of the helical wind turbine is also higher 2%-3% than that of the H type wind turbine, and especially in the case of low tip speed ratio, the gap is more obvious. These experimental results support the conclusion that a helical wind turbine has better aerodynamic performance and start-up performance.