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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.

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Within the present publication, the rotor head of a compound helicopter known as Rapid And Cost-Effective Rotorcraft (RACER) is investigated. In particular, the aerodynamic design optimisation of the RACER blade-sleeve fairings (BSFs) is conducted. For this purpose, an isolated rotor head is generated featuring a full-fairing beanie, the BSF and a truncated rotor blade (RB). Moreover, a single RB is investigated at two different azimuthal rotor positions, which correspond to the advancing and the retreating RB case. For this purpose, an averaged circumferential velocity is determined in the blade-sleeve region and superposed with the RACER cruise speed in order to estimate the prevailing flow conditions. The automated aerodynamic design optimisation is performed by means of a previously developed optimisation tool chain. A global multi-objective genetic optimisation algorithm is applied for the given problem. During preliminary work, a 2D aerodynamic design optimisation of selected blade-sleeve sections was conducted. These optimised aerofoils represent the design variables for the current optimisation problem. The shape modification of the 3D fairing is realised by exchanging specific aerofoils at certain spanwise sections.

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