Performance optimization of a high-aspect-ratio fan blade using lean, sweep, and chord techniques

In this paper, the aerodynamic performance of a three-dimensional civil turbofan fan blade is enhanced through a coupled numerical framework integrated with advanced optimization algorithms, yielding a refined, state-of-the-art blade design. Numerical investigations targeting performance improvements in high-bypass-ratio fan stages with comparable specifications have been scarcely reported in previous literature. Distinctively, the present study simultaneously alters blade lean, sweep, and axial chord distribution to achieve superior aerodynamic characteristics. The influence of these geometric modifications on the fan performance map is evaluated at the design point of the engine thermodynamic cycle, demonstrating measurable improvements in both thrust generation and specific fuel consumption. The aerodynamic behavior of the JT9D-7 fan blade is simulated numerically, and comparison against available experimental data exhibits strong agreement, thereby validating the computational methodology. Furthermore, the impact of two mid-span shrouds on the fan characteristic curves is examined in detail. Blade lean, sweep, and the chord distribution from hub to shroud are considered as key design variables. The optimization objective focuses on enhancing on-design performance indicators, including total pressure ratio, isentropic efficiency, and mass flow rate. The Taguchi method was employed to evaluate the sensitivity of the objective functions to variations in the selected design parameters. The L-16 and L-32 two-level orthogonal arrays were utilized to construct the targeted simulation matrix. The results indicate that blade lean angle exerts the greatest influence on isentropic efficiency, whereas mass flow rate is more strongly affected by blade sweep angle. Subsequently, a coupled framework integrating a genetic algorithm with an artificial neural network surrogate model was implemented to perform both single-objective and multi-objective optimization of the aerodynamic flow field and fan performance metrics. According to the multi-objective optimization results, the best-case design achieved improvements of 0.8%, 0.89%, and 0.897% in total pressure ratio, isentropic efficiency, and mass flow rate, respectively, at the design point. Finally, mid-span shrouds were applied to the optimized configuration, and its performance map was compared with that of the baseline fan blade equipped with the same shrouds. The comparison confirms a noticeable enhancement in operating parameters. In the second phase of this study, the impact of the improved design-point performance of the optimized fan blade on the thermodynamic cycle of an unmixed-flow turbofan engine was assessed. The results demonstrate that, for the best optimization case, thrust and specific fuel consumption improved by approximately 1.207% and 1.816%, respectively, relative to the reference engine.