| The Actively Controlled Tip (ACT) is a mechanism which is designed to displace the blade tip vortex and by this, to reduce rotor Blade Vortex Interaction (BVI) noise. In order to achieve this objective, the centrifugal loads and the aerodynamic loads are numerically calculated and designed reversely to find the compulsory torque needed to deflect the blade tip from zero degree to 20 degrees. The novelty of the ACT is the counter-weight concept using a screw-jack mechanism. The key idea of the counter-weight concept is to allow the blade tip to rotate freely without any load from zero degree to 10 degrees, beyond which point, the actuator power will help to complete the blade tip motion down to 20 degrees. The ACT demonstrator was fabricated and tested on the whirl tower in DLR (German Aerospace Centre). The ACT demonstrator was successfully tested and it deflected full 20 degrees in about one minute at 400 RPM but it failed at 700 RPM. An extensive analysis of the cause of the ACT failure is presented and recommendations are given to improve the design. Furthermore, the self-locking system was designed in order to test the feasibility of having the ACT on the rotor blade tip. |
