A Rigid Body Model For Analysis Of Aerogenerator Rotor Dynamics

The design of large scale wind turbines will more than likely be governed by the unsteady vibratory loads which can be aerodynamic, gravitational, and inertial in origin. This study uses a fundamental but simple rigid body model of an aerogenerator to explore some of the dynamic problems of design and operation of such a machine. The simple rigid body model includes dynamic interaction among gravitational, kinematically induced, and elastic support forces. Past experience in the helicopter industry and physical intuition indicate that the coupling of rotor flapping vibrational modes together with the tower translational motion would be a key vibrational consideration. For this reason, this particular study focuses directly and in as simple a manner as possible on this mode of response. The primary effort is to identify the important parameters and demonstrate their influences in a direct and simple manner. It is possible to examine this type of response using one of many finite element computer programs. However, that type of study requires the interpretation of a large number of computer runs before the roles of various design parameters can be assessed. On the other hand, the results of this study are applicable to a very broad spectrum of configurations and the closed form solution readily yields important design and operation guidelines. Unfortunately, the simplified model does not answer all of the important questions and at some stage of the design more detailed models such as finite element schemes must be used. It is hoped that the use of this simple model will allow later studies to focus more directly on some of the more complex dynamic problems. With this objective in mind, aerodynamic forces, and output shaft coupling torques have been excluded from the analysis.