无轴轮缘导管涡轮机水动力学性能研究

Study on hydrodynamic performance of shaftless rim-driven ducted turbines

无轴轮缘导管涡轮机作为一种新概念潮流能发电装置,具有诸多优点且应用前景广泛。采用计算流体力学(CFD)方法对无轴轮缘导管(SRD)涡轮机与传统有轴导管涡轮机进行了数值模拟对比研究,分别考察了两者水动力学性能的差异及叶轮轮径比对无轴轮缘导管涡轮机水动力学性能的影响。研究结果表明:在一定轴径比范围内,无轴轮缘导管涡轮机相比有轴导管涡轮机具有更高的输出功率及更低的轴向推力,但其瞬时功率及轴向推力的波动振幅相比有轴导管涡轮机略微增大,且随着叶轮轴径比的减小,其波动振幅进一步呈现出增大的趋势。此外,由于无轴轮缘导管涡轮机在轴心处存在一定面积的扫掠缺口,压力差将迫使水流通过轴心缺口"泄漏"出去,形成轴心射流,使其尾流恢复速度明显快于有轴导管涡轮机,且随着叶轮轴径比的减小,尾流恢复速度也进一步加快。研究成果为无轴轮缘导管涡轮机的优化设计及工程应用提供了一定的参考依据。

As a new concept of tidal current power generation device,the shaftless rim-driven ducted(SRD)turbine has many advantages and a wide application prospect.We apply a computational fluid dynamics(CFD)method to simulations and a comparative study of this type of turbine and the conventional shaft ducted turbine,focusing on the differences in hydrodynamics between these two ducted turbines and the influence of shaft diameter ratios on the SRD turbine.The results show that in a certain range of shaft diameter ratios,the SRD turbine has a higher output power and lower axial thrust than those of the shaft ducted turbine.However,the fluctuation amplitudes of its instantaneous power output and axial thrust are slightly larger,and they further increase with a decreasing shaft diameter ratio.We find that for the SRD turbine with a swept gap of a certain size,pressure will force water to"leak"through the gap forming an axial jet.This will result in a significantly higher wake recovery rate that is further accelerated with a decreasing shaft diameter ratio.