阻力型水平轴水轮机水动力及尾流特性分析

水轮机是水能利用与水力发电的核心技术装备。传统的升力型水平轴水轮机需满足一定流速条件才可获得既定的效率，因此该型水轮机并不适用于流速较低的区域。为了拓展水平轴水轮机的适用范围，依据阿基米德螺旋线原理，设计了两种具有不同旋叶倾角的新型阻力型水平轴水轮机，并采用计算流体力学方法对二者的水动力及尾流特性进行了三维数值模拟研究。结果表明，变角水轮机在尖速比为0.5～2.0的范围内具有更高的功率系数，且其峰值功率系数相比定角水轮机提升了16%。此外，与一些文献中所报道的升力型水轮机在尖速比为0.5～2.0的范围内相比，变角水轮机也具有较高的功率系数。以尖速比为1.5为例，其功率系数相比至少提升了60%以上。与此同时，变角水轮机在全尖速比范围内具有更低的推力系数，但其性能波动比定角水轮机要明显。流场分析显示，两种阻力型水平轴水轮机的后方均出现了呈环状螺旋形的叶尖涡带和呈条状的毂涡带，而变角水轮机的叶尖涡带和毂涡带的连续性更强，向下游发展的轨迹也更长。此外，变角水轮机的尾流恢复比定角水轮机更快。研究结果揭示了阻力型水平轴水轮机的水动力及尾流特性，为其优化设计和推广应用提供了一定的参考依据。

Analysis of hydrodynamic and wake characteristics of drag-type horizontal axis hydraulic turbines

Hydraulic turbine is the core equipment for hydropower utilization. The traditional lift-type horizontal axis hydraulic turbine needs a certain flow velocity to obtain an established efficiency, and thus is not suitable in the cases of low flow rates. To expand the application scope, we design two new drag-type horizontal axis turbines with different propeller blade angles based on the Archimedes spiral principle, and investigate their hydrodynamic performance and wake characteristics using the computational fluid dynamics method. The results show that these variable angle designs have larger power coefficients in the tip speed ratio range of 0.5 to 2.0, and their peak value is up to 16% larger than that of the fixed angle. And the power coefficients are also larger than those of lift-type horizontal axis turbines reported previously in the literature; the coefficient is increased by at least 60% at the tip speed ratio of 1.5, for instance. Meanwhile, the variable angle turbine has a smaller thrust coefficient in the whole tip speed ratio range, while its performance fluctuation is more obvious than that of the fixed angle. Flow field analysis reveals that annular spiral tip vortices and strip-shaped hub vortices develop behind the two drag-type horizontal axis turbines, and the variable angle designs make the tracks of tip vortices and hub vortices more continuous and extend longer into the downstream. In addition, the wake recovery of the variable angle turbines are much faster than that of the fixed angle. The results reveal the hydrodynamic and wake characteristics of our drag-type horizontal axis hydraulic turbines, which can be referred to in their optimal design and application promotion.