轴流式水轮机导流罩与叶轮尾流流场仿真研究

Numerical analysis of flow inside and behind diffuser concerning an axial-flow tidal current turbine

文中提出一种新型轴流、悬浮式潮流能水轮机结构,为提高其潮流能利用效率,采用CFD技术对水轮机外围流线型导流罩内流场与叶轮尾流场进行数值仿真研究。通过对比拟定的10种不同线型导流罩,发现收缩段和扩散段的进出口曲线前后连接点比例mx为0.3的双三次曲线导流罩内流场更加稳定、均匀。为进一步研究导流罩的聚能作用与叶轮尾流场的速度分布情况,实施了有、无导流罩工况下水轮机的数值仿真,结果显示:距离叶轮下游边缘1.25D(D为叶片直径)以内的流场域流速有显著的改变,且加装双三次曲线0.3mx=线型导流罩,水轮机较敞水工况输出功率提高约29%。相关的拖曳水池模型试验验证了数值仿真方法的有效性。

A suspending type axial-flow turbine system has been developed in this paper. The hydrodynamics of its diffuser and rotor have been investigated by CFD methods, aiming at improving the power conversion efficiency of the turbine system.Through comprehensive comparison among ten kinds of diffusers, it has been found that the flow inside diffuser with 0.3mx = cubic curve is more steady and uniform superior to others. In order to investigate the flow characteristics in the wake behind turbine and the power conversion effect of turbine, the comparison between turbines with and without diffuser has been carried out. Based on the case of 0.3mx = cubic curve diffuser, it has been found that the downstream velocity of the rotor has obviously changed in the distance less than 1.25 times of blade diameter, and the output power of the turbine system surrounded by diffuser is about 29% larger than that relating open water. A model test has been carried out, and the efficiency of the proposed CFD numerical simulation has been verified.