Design Case for a Mach-scaled Model Blade SMART ACTUATION MECHANISMS FOR HELICOPTER BLADES DESIGN CASE FOR A MACH-SCALED MODEL BLADE

On the cover: Representation of the flow around a helicopter blade with a Gurney flap. Summary Today's helicopters are the result of collaborative work in mechanical engineering and aeronautics. The European project " Clean Sky " aims at improving the efficiency and the global transport quality of aircraft. In the field of rotorcraft, the research in this project is currently focussing on active blade systems to adapt the aerodynamic properties of the blade to the local aerodynamic conditions. Fuel-efficiency, reduction of vibration and noise and increase of the helicopter maximum speed are the benefits expected from these new technologies. To envision the implementation of these innovative blade concepts, this thesis investigates the selection process for actuators, the methods to design and optimise actuation systems and the procedures to validate them through simulations and testing. Integrating an actuation system in helicopters is especially difficult because of a combination of challenges. To begin with, these include the tremendous loads due to the rotation of the blade, the limited space available, and constraints regarding durability. Secondly, the impact that the actuation system will have on the rotor blade behaviour has to be taken into account. And lastly, integrating the component inside the actual structure of a rotor blade should be feasible. A system based on piezoelectric actuators provides a potential solution to meet these challenges. A selection process has been established in Chapter 2 to match an actuation technology to application requirements. For the actuation of helicopter active systems, high performance " Macro Fibre Composite " actuators and Physik Instrumente patch d 33 actuators turned out to be the best choice. The tests discussed in Chapter 3 showed the superior properties of the d 33 patch actuator v vi SUMMARY from Physik Instrumente for the purpose of integration inside a rotor blade. Among many of the smart blade concepts under development, the active Gur-ney flap is considered in the framework of the Clean Sky Innovative Technology Development project " Green Rotor Craft " , for its potential impact on the blade performance and technology readiness. Actively deploying the Gurney flap on the retreating side of the helicopter increases the lift of the rotorcraft and its overall performances. To validate this technology, numerical studies and wind-tunnel testing on reduced-scale rotor blades are necessary. The procedures detailed in this work are applied to the design of an actuation system to fold and deploy a Gurney …