Dynamische Vorauslegung eines Rotorblattes auf Basis des Rotorblattgenerators

Abstract

The optimization of a rotorcraft is a complex multidisciplinary process that includes the profile selection, the rotor blade geometry and the structural design of a rotor blade. The motivation of this master thesis is to contribute to the development of a process chain that combines aerodynamics, structure and dynamics and creates the basis for a fully automated rotor blade optimization. For this purpose, the rotor blade generator developed in the DLR project VikToria will be extended within this master thesis, so that a rotor blade design developed in the DLR project FTK can be mapped with it. Moreover, the system structure of the rotor blade generator is modified to allow flexible parameter control based on a rotor blade input file. To realize the dynamic FEM-Analysis of a rotor blade based on the previously calculated 2D rotor blade cross sections, an interface to the DLR's own softwaretool FEM was programmed. This also includes the implementation of an automated generation of the input file required for the FEM analysis. Based on the previously chosen geometric parameters a sensitivity analysis was carried out. In regards to this the structural properties of the rotor blade cross sections under the influence of the parameter variations were deterined. These are used to identify the first suitable optimization parameters in advance and check whether their influence on structural properties such as stiffness is significant. As it turned out the parameter of the Skin and the spar have the biggest influence in regards to the increase of stiffness. For the torsion cap a significant effect on the torsional stiffnes can not be observed. Because of the enlargement of the balance weight a positive effect on the location of the denter of gravity can be determined. To evaluate the dynamic blade properties, these are calculated in a further parameter study under the influence of defined extremes. During the evaluation of the dynamic properties the effects on the system behavior of a rectangular rotor blade was determined and areas of resonance couplings to be avoided with different eigenmodes and the speed multiples are identified. In regards to this it turned out that because of the limitations again the numer of parameters were reduced. The greatest scope for parameter variation is the length extension of the spar in direction of the profile chord. Because of the maximization of the distance between leading edge and spar trailing edge the biggest increase of stiffness in regard to the flap und lead lag motion can be reached.