翼型弦长和方位角对垂直轴水动力转轮启动性能的影响

Effects of chord length of hydrofoil and azimuth angle on startup performance of vertical⁃axis hydrokinetic rotor

针对H型水动力转轮启动力矩小、启动时间长的问题,运用计算流体动力学方法进行了模拟与分析.采用6DOF模拟转轮转速随作用力矩的变化过程,对转轮在不同初始角度条件下启动时的瞬态流场、角速度与输出力矩进行了对比与关联分析.结果表明,直叶片垂直轴水动力转轮启动过程中,角速度与输出力矩的变化之间无显式相关性.在最小静力矩条件下启动时,转轮到达角速度和力矩峰值所需的时间较在最大静力矩条件下启动时间长.到达最大转轮旋转角速度时,各叶片内侧存在较大低压区,这一点不受启动角度变化的影响.当叶片包围区域内低速区面积大时,转轮的输出力矩较小.在最大静力矩条件下启动时,尾流区的完整性较强.在不同翼型弦长条件下,角速度经历了上升、下降、再到平稳振荡的过程.随着翼型弦长自0.16 m增大至0.24 m,转轮启动时间增加0.63 s,转轮旋转达到稳定后的平均角速度变小,但角速度波动幅度基本不变.

To solve the problems of small startup moment and long startup time of the H⁃type hydrokinetic rotor,the simulation and analysis were conducted by the computational fluid dynamics method.The six degree of freedom(6DOF)method was adopted to model the variation of rotational speed of rotor with the torques acting on rotor.Comparison and correlation analysis were conducted among transient flows,rotational speed and output torque at different initial setting angles.The results show that there is no explicit correlation between rotational speed and output torque during the startup process of the vertical shaft hydrodynamic rotor with straight blade.As the rotor starts up at the minimum static torque,the time required to reach the maximum rotational speed and output torque is longer than that associated with the maximum static torque.As the maximum rotational speed is attained,low⁃pressure zones are produced in the area enclosed by the blades,which is insensitive to the initial setting angle.Large area of low⁃pressure zones is responsible for low output torque.As the rotor starts up at the maximum static torque,the integrity of the wake flow is relatively high.The rotational speed experiences increasing,decreasing and subsequent regular oscillation,which is common at different chord lengths of the airfoil.As the chord length is increased from 0.16 m to 0.24 m,the startup time is extended by 0.63 s,and the average rotational speed is decreased for the stabilized rotation,but the fluctuation amplitudes remain nearly invariant.