On the Effectiveness of Low-Fidelity Optimization Methods for Propeller Design

This paper presents a novel optimization framework based on Blade Element Momentum Theory (BEMT) for the blade shape optimization of the Clark-Y 5868-9 low-speed NACA propeller. An in-house BEMT solver is validated against experimental data. The objective of the optimization is to maximize propeller efficiency through an iterative coupling of planform and sectional optimizations. For planform design, an evolutionary algorithm is employed to optimize the pitch angle and chord spanwise distribution. For sectional airfoil optimization, a gradient-free method minimizes the drag coefficient under local flow conditions. The aerodynamic performance of the airfoils is determined using XFOIL. The rotor efficiency of the optimized geometry increased by 5.9%, relative to the baseline propeller. The chord lengths increased in the root region and decreased towards the tip, whereas the pitch angles enlarged. The optimized sectional airfoils present higher thickness and lower camber compared to the baseline Clark-Y airfoil. The results are discussed to evaluate the effectiveness of this low-fidelity approach for rotor blade shape optimization in the preliminary design phase.