Development of an innovative double-swept rotorblade tip for the rotor test facility Goettingen

Innovative double-swept rotor blade tip planforms show significant potential to reduce noise and vibrations while improving the overall performance. Current test results for a non-rotating double-swept innovative rotor blade tip model, inspired by the DLR patent Erato, were obtained in a conventional wind tunnel (DNW TWG, Transonic Wind Tunnel Goettingen) under forced pitching motions. In the next step, the influence of rotation and the environment of an entire rotor head system should be considered. It is of great interest to investigate the influence of rotation on the aeroelastic behaviour and the unsteady aerodynamics in a dedicated further experiment. The Rotor Test Facility Goettingen (RTG) was built for research on rotating rotor blades under optimized boundary conditions and will be used for the planned experiments. Typical flow phenomena associated with rotor blades will be investigated, such dynamic stall, compression shocks as well as aeroelastic stability. For that purpose new innovative double-swept rotor blades for the RTG have been developed at the DLR Institute of Aeroelasticity in Goettingen. The design of the planform is partially based on the existing wind tunnel model. Further profile sections and a rotor head attachment were added. Design load cases were determined from two dimensional numerical flow simulations regarding several rotor blade sections. A finite element analysis, including fatigue analysis, was carried out as well. In order to extract the dominant flow phenomena the rotor blades are instrumented with unsteady pressure transducers, temperature transmitters and strain gauges. The acquired data will enable subsequent evaluation concerning aeroelastic stability of the entire rotor head system and the rotor blade tip geometry. Furthermore the influence of rotation on the dynamic stall phenomenon can be assessed.