前弯型叶片液力透平的数值计算

为研究具有前弯型叶片液力透平的性能,设计了3种不同比转数具有前弯型叶片液力透平.采用全流场和结构化网格技术对液力透平内部流动进行数值计算,分析了具有前弯型叶片液力透平在不同流量下的外特性、压力场和速度场,得到了液力透平叶轮和尾水管内部流场随流量变化规律.研究结果表明:透平内部压力场从蜗壳进口经叶轮到尾水管出口压力逐渐减小,随流量的增大,液力透平的进出口压差逐渐增大;在前弯型叶片工作面存在旋涡区域,旋涡位置和区域大小随着流量的变化而变化;在尾水管横截面上存在随流量而变化的圆周速度分量;叶轮内部的水力损失是前弯型叶片液力透平内部的主要的水力损失,在3种液力透平中都占总水力损失的60%以上,并随比转数增大而逐渐增大.因此,前弯型叶片液力透平的优化设计应主要集中在叶轮研究.

Numerical simulation of hydraulic turbines with forward-curved blades

The impellers of centrifugal pumps with three different specific speeds were designed with forward-curved blades to study their performance as turbine. Then, the whole internal flow filed in these hydraulic turbines were calculated with structured mesh technique. The performance curves, pressure and velocity fields at different flow rates were analyzed, and the variation of flow field in the impeller and draft tube with flow rate was obtained. The results show that the fluid pressure steadily decreases from the volute inlet to the impeller and draft tube outlet, and the pressure difference between the inlet and the outlet of hydraulic turbine increases gradually with increasing flow rate. A vortex region is found near the blade pressure side, and its position and size vary with flow rate. There is a peripheral velocity component in the cross-section of draft tube, its magnitude varies with flow rate. The hydraulic loss inside a hydraulic turbine with forward-curved blades mainly occurs in the impeller and accounts for more than 60% of the total hydraulic loss for three hydraulic turbines, further the percentage rises with increasing specific speed. Therefore, the optimization design of hydraulic turbine with forward-curved blades should be focused on the impeller.