Preliminary Aerodynamic Design Strategy for Prop-Rotors Based on Multifidelity Methods

Abstract

A design strategy to provide suitable baseline prop-rotors for sophisticated applications is presented. Unlike those approaches aimed at improving the aerodynamic performance of an already refined blade by high-fidelity methods, the new strategy can efficiently work out proper configurations with no baseline. It is introduced through the design process of the initial blades for a small uncrewed tilt-rotor aircraft. Moreover, the strategy consists of four main parts, including identifying ideal boundaries for chord and twist distributions under the theory of minimum energy loss, building surrogate models based on a low-fidelity aerodynamic method, conducting a multi-objective optimization within the ideal boundaries, and finally, selecting feasible configurations on the resulting Pareto front through a high-fidelity aerodynamic method. Under the given design requirements, a representative configuration can achieve a figure of merit around 0.7 and a cruise efficiency of more than 0.6, acceptable for its size. This strategy is beneficial for customizing prop-rotors in industrial applications and effectively shrinking design spaces for more advanced optimizations. The design process revealed that a highly twisted root could help boost the cruise efficiency at the design point by evening the span-wise loading and mitigating the induced vortex near the root. Narrowing the loading gap between the two design states might help obtain a higher cruise efficiency from the design planning level. Moreover, solely using the infilling scheme of expected improvement could impair surrogate models’ global accuracy and further impact the selection of optimal configurations in a multi-objective optimization problem; thus, a mixture of multiple infilling criteria may be worth trying.