冲击式水轮机水斗根部的工艺性结构优化

Structural Optimization for Bucket Root of Pelton Turbine Based on Manufacturability

针对冲击式水轮机水斗根部难于加工的问题,根据水斗结构复杂和开放性差的特点,对水斗数控加工中遇到的被加工表面曲率过大以及刀具与被加工面干涉造成的铣刀长径比过长,难于实现加工的情况,以某冲击式水轮机转轮结构为基础,对水斗根部卸荷面附近区域进行结构优化.建立了水斗有限元分析模型,计算并施加等效的边界条件和载荷.有限元分析结果表明:水斗e方案平均应力小于许用值60 MPa,交变应力幅值小于许用值30 MPa;且该方案满足数控可加工性和水斗强度要求.

Structural optimization for area near unloading surface of bucket root is studied, since the bucket root of Pelton turbine is difficult to process. Because of the very large curvature of work piece＇s surface and very large length to diameter ratio caused by interference between cutting tool and work piece＇s ~urface, the numerical control machining is impracticable. Based on high structural complexity and lack of openness of bucket, measures that could solve the machining problem are deeply analyzed. According to a Pelton turbine runner structure, struc- tural optimization is implemented for the area near unloading surface of bucket root. Finite element model is estab- lished and boundary condition and loading are calculated and applied to the model. The results of finite element a- nalysis show that the equivalent average stress of bucket for scheme e is smaller than the allowable value about 60MPa, and alternating stress amplitude of it is also less than the allowable value about 30MPa. Then, the struc- ture of scheme e that meets the strength requirement and improves the numerical control machining manufacturabili- ty is obtained.