A Novel Design Method for Electric Aircraft Propulsors

This paper presents a unified methodology for designing open propellers and ducted fans. By reformulating momentum theory in terms of velocity ratios, new design variables are introduced that complement parameters traditionally used in turbomachinery design. These metrics provide designers with an intuitive framework for parameterizing both the internal and external flowfields of a propulsor. Because this framework incorporates non-dimensional metrics commonly used in the turbomachinery design process, it allows designers to generate propulsors that are within well-established aerodynamic feasibility limits. This aerodynamic framework is integrated into a comprehensive design method that includes meanline analysis, spanwise flowfield specification, and an inverse-design approach for airfoil generation. The inverse method is based on a precomputed database of airfoil sections and is compatible with a wide range of operating conditions, including inlet angles, row velocity ratios, Mach, and Reynolds numbers. In addition to providing the required geometry, the method also provides airfoil performance metrics and predicts the entire blade-to-blade flowfield. This design process offers a fast, flexible, and intuitive approach for generating initial designs of open propellers and ducted fans. Additionally, it provides insights into the aerodynamic necessity of propulsor ducting in different design scenarios. To validate the methodology, two low-speed case studies are presented: one for an open propeller and another for a ducted fan. The resulting 2D blade-to-blade flowfields are compared against full 3D RANS simulations.