异步反转式组合型垂直轴水轮机性能研究

Study on performance of an asynchronous reverse-type combined vertical axis hydrokinetic turbine

为了解决升力型垂直轴水轮机因其较低的静力矩而无法应用于低流速海流环境的问题,提出一种内外转子异步反转的组合型水轮机。装置的外部是H型转子,内部采用Savonius型转子,2个转子在各自最优尖速比下运行,在提供运行效率的同时降低系统启动流速。利用CFD软件数值分析内部转子的转速、组合轮机的直径比对外部H型转子及组合轮机性能的影响规律。采用数值计算方法研究组合轮机在不同来流方向的静力矩系数。研究结果表明:当直径比小于0.4时,内部转子的尖速比几乎不影响外部H型转子的效率,但当内部转子尖速比大于0.5时,内部转子转换为耗功部件,组合轮机的效率降低;由于内外转子存在转速差,大直径比组合轮机的内外转子将产生较强的相位干涉,增加外部转子的扭矩波动,会降低组合轮机的寿命。因此,组合轮机的直径比应选择为0.2~0.4,内部S型转子尖速比为0.2~0.5。组合轮机在大部分流动方向下,静力矩系数显著提升。

A novel design featuring a combined vertical axis hydrokinetic turbine,incorporating asynchronous reverse rotation of inner and outer rotors,was proposed to overcome the issue of low static torque,a limitation that restricts the use of lift-type vertical axis hydrokinetic turbines in low-speed marine environments.This combined turbine incorporates asynchronous reverse rotation of inner and outer rotors,where the external rotor is an H-type,while the internal rotor adopts the Savonius configuration. This arrangement ensures that both rotors operate at their optimal tip speed ratios, thereby maximizing operational efficiency while reducing the startup flow velocity of the system. Computational fluid dynamics software was employed to analyze the influence of the tip speed ratio of the internal rotor and the diameter ratio of the combined turbine on the performance of the external H-type rotor and the combined turbine. The static torque coefficient of the combined turbine at different flow angles was investigated by the numerical calculation method. The results show that when the diameter ratio is less than 0.4, variations in the tip speed ratio of the internal rotor have minimal impact on the efficiency of the external H-type rotor. However, as the tip speed ratio of the internal rotor exceeds 0.5, it starts to consume more power, resulting in a decrease in the overall system efficiency. Additionally, flow field analysis reveals that due to the differing rotational speeds of the internal and external rotors, a higher diameter ratio in the combined turbine leads to pronounced phase interference between the two rotors. This interference causes increased torque fluctuations in the external rotor and shortens the operational lifespan of the device. Therefore, a diameter ratio ranging from 0.2 to 0.4 and a tip speed ratio of the internal Savonius rotor between 0.2 and 0.5 are recommended. The combined turbine exhibits a significant increase in static torque coefficient in most flow directions.