Improved propeller designs are necessary to ensure an eco-friendly and resource-saving operation. The shape optimization of propellers involves different disciplines, which include the aerodynamics and the structural characteristics of the propeller. The requirements of the individual disciplines for the propeller design are contradictory and compromises must be made. To deal with this complex optimization task, a modular multi-disciplinary optimization framework is developed. The framework is based on a Python control script, which invokes the individual analysis modules. Within the framework, a blade element momentum theory approach for the aerodynamic analysis and a finite element method for the structural analysis are used. This allows for an efficient calculation of various designs. In a first step, a pure aerodynamic optimization is conducted. In a second step, structural constraints in form of the permissible material stress and the propeller blade tip deflection are considered. The results are compared to a design method, which calculates the blade shape for minimal induced losses.

The present work is part of the Clean Sky 2 project Full-Fairing Rotor Head Aerodynamic Design Optimization (FURADO), which deals with the aerodynamic design optimization of a full-fairing rotor head for the Rapid And Cost-Effective Rotorcraft (RACER) compound helicopter. The rotor head is a major drag source and previous investigations have revealed that the application of rotor head fairings can be an effective drag reduction measure. As part of the full-fairing concept, a new blade-sleeve fairing was aerodynamically optimized for cruise flight. Within this publication, the newly developed blade-sleeve fairing is put to test on an isolated, five-bladed rotor head and compared to an already existing reference blade-sleeve fairing, which was developed at Airbus Helicopters. Numerical flow simulations are performed with ANSYS Fluent 2019 R2 considering a rotating rotor head with cyclic pitch movement. The aerodynamic forces of the isolated rotor head are analyzed to determine the performance benefit of the newly developed blade-sleeve fairing. A drag reduction of 4.7% and a lift increase of 20% are obtained in comparison to the Airbus Helicopters reference configuration. Furthermore, selected surface and flow field quantities are presented to give an overview on the occurring flow phenomena.