三齿枞树型叶根轮槽型线优化设计

Optimization on Groove Profile in Trident Fir-Tree Blade Root

汽轮机末几级长叶片的叶根轮槽强度,对于汽轮机运行的安全性而言至关重要。对现有的三齿枞树型叶根轮槽型线进行了优化,并对优化后叶根轮槽的应力分布进行分析,对比了叶根的应力集中因数,评估了叶根轮槽相对滑移量以及叶片振动频率的变化,分析了叶根与轮槽的配合间隙,绘制出了优化后的叶根轮槽型线图。结果表明,优化后叶根的峰值应力与优化前相当,内弧侧与背弧侧的应力水平趋于一致,轮槽的峰值应力明显下降,叶根的应力集中因数均布情况有所改善,优化方案对叶片的振动频率影响较小。优化方案能够明显改善叶根轮槽的强度,并已成功用于已投运的实际工程项目。研究成果可为高转速汽轮机末几级长叶片的结构设计提供参考。

The root and groove strength of last-stage blades is significant to the operation safety of steam turbine.The existing groove profile in trident fir-tree blade root was optimized,and the root stress distribution of the optimized one was analyzed.The stress concentration factor was calculated,and the relative displacement of root and groove was evaluated.Meanwhile,the blade frequency was calculated,and the clearance between root and groove was checked,so that the drawing of optimized groove profile of blade root was obtained.The results show that the root peak stress of the optimized one equals to that of the former,the stress of concave side and convex side of blade converges gradually,and the groove peak stress decreased obviously.After optimization,the distribution of root stress concentration factor was improved,and the blade frequency only changed a little.The root and groove strength of the optimized one has been improved obviously,and its application in several units is successful.The research results can provide reference for the design of last-stage blades in steam turbines with high rotating speed.