Aerodynamic–Aeroelastic–Structural Multidisciplinary Optimization of Transonic Compressor Rotors Using DFFD, Pre-NSGA-II, and Harmonic Balance

This study develops an aerodynamic–aeroelastic–structural optimization framework for transonic axial compressor rotors that are prone to flutter. The main novelty of the framework is the integration of directly manipulated free-form deformation (DFFD), a pre-screening surrogate-assisted multi-objective genetic algorithm (Pre-NSGA-II), and a harmonic-balance-based energy method. DFFD enables flexible, low-dimensional control of blade deformation, while the pre-screening strategy reduces the number of expensive high-fidelity evaluations required during optimization. Using the proposed framework, a transonic compressor rotor is optimized to maximize the design-point isentropic efficiency and aerodynamic modal damping ratio while minimizing the maximum blade stress. The optimization process simultaneously considers blade geometry, the meridional flow path, and tip clearance. After optimization, the isentropic efficiency increases by 1.40 percentage points, while the mass flow rate, total pressure ratio, and surge margin remain within the prescribed constraints. The predicted flutter boundary shifts toward the surge boundary at 80%–100% rotational speeds, indicating that the aeroelastic stable operating region is broadened. Meanwhile, the maximum von Mises stress decreases from 707.4 MPa to 671.0 MPa. These results indicate that the proposed multidisciplinary optimization framework provides a practical and computationally efficient route for balancing aerodynamic performance, aeroelastic stability, and structural integrity in compressor rotor design.