ABSTRACT

Installing a turbine in a duct generally increases the flow through the rotor. If there is flow confinement due to limited water depth, the presence of lateral boundaries, or the presence of adjacent turbines, a further flow enhancement through the rotor will be achieved. Extensive studies of ducted turbines in uni-directional flow have shown that rotor-based power coefficient$C_p$can exceed the Betz-Joukowsky limit (BJL) for bare turbine, whereas the exceedance of the BJL is rarely reported for duct-area-based power coefficient $C_P^{\ast }$. In this work, CFD studies have been carried out for several flanged duct turbines with different duct geometries under bi-directional flow conditions. The actuator disc approach is used to simulate the rotor. The results show that a flanged duct turbine with an inlet-arc flap and a curved brim can achieve a maximum value of $C_P^{\ast }$ close to the BJL for flow from either direction while a symmetric duct turbine- gives maximum $C_P^{\ast }$ of about 60% of the BJL. The effect of the flow confinement on $C_P^{\ast }$ shows $C_P^{\ast }$ increases with blockage ratio$ϵ$ and a little variation in the relative performance of ducted and bare turbines. $ϵ$. The findings pave the way for the realization of turbines with a flanged duct.

摘要

将涡轮机安装在管道中通常会增加通过转子的流量。如果由于有限的水深，存在侧向边界或存在相邻的涡轮而存在流量限制，则将实现通过转子的进一步流量增强。管道式涡轮机在单向流动中的大量研究表明，基于转子的功率系数$C_p$可以超过裸机涡轮的Betz-Joukowsky极限（BJL），而基于风道面积的功率系数很少报道超过BJL $C_P^{\ast }$。在这项工作中，已经在双向流动条件下对具有不同管道几何形状的几台法兰管道涡轮进行了CFD研究。执行器圆盘方法用于模拟转子。结果表明，带有进气弧瓣和弧形边缘的法兰风轮机可达到最大值$C_P^{\ast }$ 靠近BJL以便从任一方向流动，而对称风轮机则可提供最大的流量 $C_P^{\ast }$约占BJL的60％。流量限制对$C_P^{\ast }$ 表演 $C_P^{\ast }$ 随阻塞率增加$ϵ$ 导管式和裸露式涡轮机的相对性能略有变化。 $ϵ$。这些发现为带法兰管道的涡轮机的实现铺平了道路。