Abstract The present study aims to reveal startup characteristics of a drag-type rotor as it is used to harness kinetic energy of flowing water. The rotational speed of the rotor and the hydraulic loads exerted on the rotor were correlated. After being validated through experimental results, a numerical scheme was used to investigate instantaneous flow parameter distributions and the torque on the rotor during the startup process. Startup processes were analyzed at different initial azimuthal angles. The results show that a successful startup of the rotor is featured by two consecutive stages, an acceleration stage and a transition stage, which is then followed by periodic fluctuations of the angular velocity. The startup failure is proved at two initial azimuthal angles of 70° and 150°. The former one is associated with positive static torque coefficient. The two failed startup processes share similar rotation positions where the rotor eventually halts. During the startup process, instantaneous flow patterns differ significantly from those obtained in static state. Small torque coefficients lead to an overall attenuation of the rotational speed and are ascribed to uniform pressure distributions over each side of the blade surface.

中文翻译：

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拖曳式水力涡轮转子的瞬态启动特性

摘要 本研究旨在揭示拖曳式转子在利用流动水的动能时的启动特性。转子的转速和施加在转子上的液压负载相关。在通过实验结果验证后，采用数值方案研究启动过程中的瞬时流动参数分布和转子上的扭矩。在不同的初始方位角下分析了启动过程。结果表明，转子的成功启动具有两个连续阶段，即加速阶段和过渡阶段，然后是角速度的周期性波动。在70°和150°两个初始方位角证明启动失败。前一个与正静态扭矩系数相关。两个失败的启动过程共享相似的旋转位置，转子最终在这些位置停止。在启动过程中，瞬时流动模式与静态获得的流动模式显着不同。小的扭矩系数导致旋转速度的整体衰减并且归因于叶片表面每一侧上的均匀压力分布。