Structural and Dynamic Optimization of a Single Axial Compressor Blade Using the Gradient-Based Method

Abstract

This paper describes the development of an in-house code for sizing optimization of blades with constraints imposed on blade’s natural frequencies and static stresses. The optimization environment includes a three-dimensional parametric model of the blade, interface functions for automated execution of the static and modal finite element analyses as well as post-processing of the results, and optimization algorithm. The blade geometry is represented by section profiles at a number of span-wise stations. Each blade section profile is parametrized by nine intuitive geometric parameters which control profile thickness distribution, chord, offset, and stagger angle. Three-dimensional finite element analysis of the blade is performed using ANSYS Mechanical software package. A sequential quadratic programming technique is used to solve the nonlinear optimization problem. Sensitivity analysis is performed using the finite-difference method. Several optimization problems with different objective functions and combinations of constraints are implemented. The aerodynamic constraints are not considered directly. The blade’s aerodynamic properties are sustained by imposing tight limits on the allowable changes of design variables. Sizing optimization is performed for an axial compressor blade of a gas turbine engine. The results show that the code can meet the defined objective and constraints for the most tested cases. A detailed comparison of optimized profiles with the baseline geometry is provided.