Performance improvement of a compound helicopter rotor head by aerodynamic design optimisation of a blade-sleeve fairing

Abstract

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.

Numerical Investigation of an Optimized Rotor Head Fairing for the RACER Compound Helicopter in Cruise Flight

“…The present work is part of the Full-Fairing Rotor Head Aerodynamic Design Optimization (FURADO) project, which is well aligned with the required innovation for high-speed rotorcraft. The project is aimed on the aerodynamic design optimization and flow analysis of a semi-watertight full-fairing rotor head with respect to drag reduction of the RACER compound helicopter [21][22][23]. Figure 2 shows the comparison between a fully articulated Airbus Helicopters H175 rotor head without fairings and the RACER full fairing.…”

“…For this purpose, a database of optimized airfoil shapes was developed for selected radial sections of the fairing [22]. Moreover, the best performing airfoils were used as the basis for the three-dimensional design optimization using a genetic optimization algorithm [23]. The objective functions were to reduce the drag on the retreating rotor blade and to increase the lift-to-drag ratio on the advancing rotor blade.…”