A Novel Multi-Level Optimization Framework for Propeller Aerodynamic Optimization

This paper presents an innovative multi-level optimization framework for blade shape design, employing an iterative full coupling between planform and sectional optimizations. Unlike conventional multi-level optimization strategies, the proposed method does not restrict sectional optimization to the geometry derived from the planform design stage. An in-house solver based on the Blade Element Momentum Theory (BEMT) is validated using available experimental and numerical data. Specifically, the proposed methodology has been tested for optimizing the Clark-Y 5868-9 low-speed NACA propeller. The optimized geometry is compared against the baseline propeller and optimal designs obtained through hybrid-fidelity and conventional multi-level optimization approaches from prior studies. Results demonstrate a 6.8% increase in efficiency relative to the baseline propeller, alongside a 0.8% improvement in thrust coefficient and a 0.9% increase in efficiency compared to an optimal design obtained with the conventional multi-level strategy. These findings highlight the capability of the proposed framework to explore design geometries beyond the limitations of traditional approaches, showcasing its potential for advancing blade shape optimization during the initial design stage.