Optimization of gas turbine fir-tree attachment based on redesigning the transition area with double-arc and spline curve

摘要

Fir-tree attachment is one of the critical regions for gas turbine service life prediction. In order to decrease the stress level of a three teeth turbine fir-tree attachment, transition area where maximum stress occurs is redesigned with double-arc and spline curve profiles. Three independent modules are developed using Matlab and the parametric design language APDL. By coupling these modules, 3-D parametric model with thermal load considered is established. In the 3-D parametric model, design variables are selected from a large number of geometry parameters, and structure is optimized automatically under constraints. It is found that the spline curve achieves the maximum equivalent stress decrease by 26.88%, followed by the double-arc with 25.31% and the single-arc with 19.83%. Optimized stress distributions indicate that the redesigns have the potential to effectively decrease the stress level. Compared with the double-arc, the spline curve shows advantages in overall stress level reduction and convergence speed. In addition, curvature radiuses of optimized shapes are extracted in order to explain the stress distribution. This analysis provides a reference for the design of fir-tree attachment.