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Performance enhancement of twisted-bladed Savonius vertical axis wind turbines
Energy Conversion and Management ( IF 10.4 ) Pub Date : 2020-04-01 , DOI: 10.1016/j.enconman.2020.112673
Ahmed S. Saad , Ibrahim I. El-Sharkawy , Shinichi Ookawara , Mahmoud Ahmed

Abstract It is important to determine the most optimal configuration of a Savonius vertical axis wind turbine that attains the best performance with a high self-starting ability. Thus, the effects of several design parameters including twist angle, overlap ratio, and endplates size ratio, along with the wind velocity on the performance of the Savonius wind turbine are investigated. Novel assessment methods based on flow field characteristics such as streamlines and pressure fields around the Savonius wind turbine are carried out. This is the first contribution to understand how geometrical variables influence the aerodynamic performance of the twisted Savonius rotor. Moreover, the variation of torque, power, thrust, and static torque coefficients are estimated. Thus, a three-dimensional, incompressible unsteady Reynolds-averaged Navier-Stokes model in conjunction with k-ω shear-stress transport turbulence model is developed. The model is numerically simulated and validated using the experimental and numerical data available in literature. Results indicate that the Savonius rotor with a twist angle of 45°, an overlapping ratio of zero, and endplates size ratio of 1.1 attains the highest net output power compared to other designs. It is found that at a wind velocity of 6 m/s, the Savonius rotor achieves a maximum power coefficient of 0.223, and with further increase of the wind velocity to 10 m/s, the power coefficient reaches 0.231. In addition, the current developed design has a positive static torque coefficient at all rotor angles, and consequently, it achieves a high self-starting ability. However, for the conventional (untwisted) design, the maximum attainable power coefficient was found to be 0.174 at an overlapping ratio of 0.15, and equal endplate size ratio. In addition, negative values of the static torque coefficient were observed at a specific range of rotor angles that prevent the self-starting ability. Accordingly, the new twisted rotor design not only enhances the power coefficient but the self-starting ability as well. The findings of the current results provide another direction for researchers and designers to utilize the twisted Savonius wind turbine.

中文翻译:

扭曲叶片Savonius垂直轴风力涡轮机的性能增强

摘要 确定具有高自启动能力的Savonius垂直轴风力发电机的最佳配置非常重要。因此,研究了包括扭转角、重叠比和端板尺寸比在内的几个设计参数以及风速对 Savonius 风力涡轮机性能的影响。新的评估方法基于流场特性,如萨沃纽斯风力发电机周围的流线和压力场。这是了解几何变量如何影响扭曲 Savonius 转子的空气动力学性能的第一个贡献。此外,估计扭矩、功率、推力和静态扭矩系数的变化。因此,一个三维,结合k-ω剪应力输运湍流模型,建立了不可压缩非定常雷诺平均Navier-Stokes模型。该模型使用文献中可用的实验和数值数据进行数值模拟和验证。结果表明,与其他设计相比,扭转角为 45°、重叠比为零和端板尺寸比为 1.1 的 Savonius 转子获得了最高的净输出功率。发现在风速为 6 m/s 时,Savonius 转子的最大功率系数达到 0.223,随着风速进一步增加到 10 m/s,功率系数达到 0.231。此外,当前开发的设计在所有转子角度均具有正静态扭矩系数,因此实现了高自启动能力。然而,对于传统(未扭曲)设计,发现最大可达到的功率系数为 0.174,重叠率为 0.15,且终板尺寸比相等。此外,在防止自启动能力的特定转子角度范围内观察到静态扭矩系数的负值。因此,新的绞合转子设计不仅提高了功率系数,而且还提高了自启动能力。当前结果的发现为研究人员和设计师利用扭曲的萨沃纽斯风力涡轮机提供了另一个方向。在防止自启动能力的特定转子角度范围内观察到静态扭矩系数的负值。因此,新的绞合转子设计不仅提高了功率系数,而且还提高了自启动能力。当前结果的发现为研究人员和设计师利用扭曲的萨沃纽斯风力涡轮机提供了另一个方向。在防止自启动能力的特定转子角度范围内观察到静态扭矩系数的负值。因此,新的绞合转子设计不仅提高了功率系数,而且还提高了自启动能力。当前结果的发现为研究人员和设计师利用扭曲的萨沃纽斯风力涡轮机提供了另一个方向。
更新日期:2020-04-01
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