水轮机转轮的三维粘性流数值计算及其结果分析

Numerical Calculation of Three-Dimensional Viscous Flow in Runner of Hydraulic Turbine

针对比转速ns为290的混流式水轮机转轮进行三维粘性流数值计算，并对计算结果作了初步分析．计算中，紊流模型采用目前国内外广泛使用的k-ε模型，流速与压力的迭代修正采用SIMPLE法．共对包括设计工况在内的8个工况点进行了流场数值计算及水力性能分析．计算表明，设计工况下的流速分布最为均匀，叶片进口边基本上为无冲角绕流，效率也最高；随着水头的提高，正冲角增加，最后在叶片背面进水边后靠上冠处产生漩涡区；而当水头相对设计水头降低时，负冲角增加，最后在叶片正面进水边后靠上冠处产生漩涡区．经分析认为这些漩涡区是非设计工况下叶道涡产生的根源，亦是水力性能下降的主要原因．此外，通过对压力系数分布曲线的分析，确定了局部低压区，从而为改型设计提供了依据．计算结果不仅能详细给出水轮机转轮内的流速和压力分布，而且能给出水轮机转轮的水力性能预估值，本计算所依赖的计算软件可成为水轮机转轮开发研究的重要手段．

Introduced in this article are the numerical calculation results and some related analyses of three-dimensional viscous flow in a runner of Francis turbine with a specific speed of 290. A widely used k-εmodel isused to determine turbulence viscosity, and velocity and pressure iterating-correction is carried out with SIM-PLE scheme. Flow fie1d numerical caculations and hydraulic per formance analyses have been conducted for 8operating-conditions, including design point. It is demonstrated by calculated results that at design point, therelative-velocity pattern is uniform,and the attacking angle at the inlet of blade is nearly zero, correspondinglythe efficiency of runner being of the highest value. Positive attacking angle increases as the water head increas-es,and finally vortex occurs near the blade inlet,the suction side and crown. On the other hand, when the wa-ter head decreases from the design head, the negative attacking-angle increases, and finally vortex also occursnear the blade inlet, the pressure side and crown. We consider that those vortexes are the cause for blade vor-tex, and contribute a lot to the hydraulic performance decreasing of turbine. Besides, local low-pressure areasare found by analyzing the curves of pressure coefficient, which will be very useful for shape-improvement ofrunner. By numerical calculations as done by us in this article, not only the velocity and pressure distributionpatterns can be gained, but the hydraulic performance, including efficiency, can also been calculated out.These programs we used in this article can further be used to the research and development of hydraulic tur-bines.