Performance improvement of a compound helicopter rotor head by aerodynamic shape optimization

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 optimization of the RACER blade-sleeve fairings is conducted. For this purpose, an isolated rotor head is generated featuring a full-fairing beanie, the blade-sleeve fairing and a truncated rotor blade. Moreover, a steady rotor is investigated and averaged flow conditions according to the RACER cruise flight are applied. The automated aerodynamic design optimization is performed by means of a previously developed optimization tool chain. A global multi-objective genetic optimization algorithm is applied for the given problem. During preliminary work, a two-dimensional aerodynamic design optimization of selected blade-sleeve sections was conducted. These optimized airfoils represent the design variables for the current optimization problem. The shape modification of the three-dimensional fairing is realized by exchanging specific airfoils at certain spanwise sections.