潮流能水轮机流场特性的数值与实验研究

NUMERICAL AND EXPERIMENTAL STUDY OF FLOW FIELD CHARACTERISTICS OF TIDAL ENERGY TURBINES

通过数值模拟和模型实验相结合的方式,研究水轮机近域的流场特性对其水动力性能的影响,分析远域下不同入流速度和尖速比等因素对尾流场特性的影响。研究结果表明,在设计尖速比下,水轮机能量转换效率的数值模拟结果(0.37)与实验结果(0.36)的误差为0.3%,水轮机阻力系数的数值模拟结果(0.73)与实验结果(0.76)的误差为-4%,验证了数值模拟方法的准确性;水轮机梢部存在明显的三维流动现象,水轮机盘前梢部存在由叶根流向叶梢的径向流速(0.24 m/s),盘后梢部存在由叶梢流向叶根的径向流速(0.14 m/s),该叶片梢部尾流区的“下洗”流速导致水轮机能量转换效率下降;入流速度不会对尾流区轴向速度的恢复产生显著影响;在近尾流区(距离盘面小于5D)随尖速比的增加,尾流区轴向速度恢复呈逐渐降低的趋势,而在距离水轮机盘面超过10D之后,尖速比不会对尾流轴向速度恢复产生明显影响,但尖速比的增加会使梢涡存在时间变短,梢涡破碎的位置更靠近水轮机盘面。

This article combines numerical simulations and model experiments to study the influence of flow field characteristics on the hydrodynamic performance of turbines in the near-field.The effect of different factors such as inflow velocity and tip-speed ratio on the wake field characteristics in the far-field is analyzed.The research results show that the relative error of power coefficient between the numerical simulation result(0.37)and the experimental result(0.36)is 0.3%at the designed tip speed ratio,and the relative error of drag coefficient between the numerical simulation result(0.73)and the experimental result(0.76)is-4%.There are significant threedimensional flow phenomena at the blade tip of the tidal turbine,there is a radial velocity(0.24 m/s)at the front of the turbine disk which flows from the blade root to the tip,and there is a radial velocity(0.14 m/s)at the rear of the turbine disk which flows from the blade tip to the root.The downwash flow velocity near the wake zone of the blade tip causes a decrease in the energy conversion efficiency of the turbine.The inflow velocity has no a significant impact on the recovery of axial velocity in the wake region;In the near wake region(within 5D distance from the disk),with the increase of tip-speed ratio,the recovery of axial velocity in the wake shows a gradually decreasing trend.When the distance from the water turbine disk exceeds 10D,the tip-speed ratio does not have a significant effect on the recovery of axial velocity in the wake.However,the increase of tip-speed ratio will shorten the existence time of the blade vortex and make the location where the blade vortex is broken closer to the water turbine disk.