It is now increasingly necessary to predict accurately, at the design stage and without excessive computer costs, the dynamic behavior of rotating parts of turbomachines, in order to be able to avoid resonant conditions at operating speeds. Classical approaches are based on different uncoupled models. For example, rotordynamics deals with the shaft behavior while bladed assemblies dynamics deals with wheels, and the possibility of interaction between those elements is generally not analyzed. In this study, the global non-rotating mode shapes of flexible bladed disc-shaft assemblies are used in a modal analysis method for calculating the dynamic characteristics (frequencies and mode shapes) of the corresponding rotating system. The non-rotating mode shapes are computed using a finite element cyclic symmetry approach. Rotational effects, such as centrifugal stiffening and gyroscopic effects, are accounted for. All the possible couplings between the flexible parts and every kind of deformations are allowed. The proposed model is applied to a thin-walled composite shaft and to a turbomolecular pump rotating assembly. The results obtained illustrate clearly some of the limitations of classical approaches.

This paper describes the development of a complete methodology for the aeroservoelastic modelling of horizontal axis wind turbines at the conceptual design stage. The methodology is based on the implementation of unsteady aerodynamic modelling, advanced description of the control system and nonlinear finite element calculations in the Samcef Wind Turbines design package. The aerodynamic modelling is carried out by means of fast techniques, such as the blade element method and the unsteady vortex lattice method, including a free wake model. The complete model also includes a description of a doubly fed induction generator and its control system for variable speed operation. The Samcef Wind Turbines software features a nonlinear finite element solver with multi-body dynamics capability. The full methodology is used to perform complete aeroservoelastic simulations of a realistic 2 MW wind turbine model. The interaction between the three components of the approach is carefully analysed and presented here.

It is now increasingly necessary to predict accurately, at the design stage and without excessive computer costs, the dynamic behavior of rotating parts of turbomachines, in order to be able to avoid resonant conditions at operating speeds. Classical approaches are based on different uncoupled models. For example, rotordynamics deals with the shaft behavior while bladed assemblies dynamics deals with wheels, and the possibility of interaction between those elements is generally not analyzed. In this study, the global non-rotating mode shapes of flexible bladed disc–shaft assemblies are used in a modal analysis method for calculating the dynamic characteristics (frequencies and mode shapes) of the corresponding rotating system. The non rotating mode shapes are computed using a finite element cyclic symmetry approach. Rotational effects, such as centrifugal stiffening and gyroscopic effects are accounted for. All the possible couplings between the flexible parts and every kind of deformations are allowed. The proposed model is applied to a thin-walled composite shaft and to a turbomolecular pump rotating assembly. The results obtained illustrates clearly some of the limitations of classical approaches.

The objective of the proposed study is to progress towards a better modeling of bladed assemblies dynamic. Coupling devices are introduced in bladed stages to increase frequencies of resonance above the range of possible excitations. Commonly they are not only used to stiffen flexible structures but also to increase damping by dry friction, reducing the amplitude of vibration. Consequently, the resulting dynamic behavior is complex and highly non linear. In order to improve numerical capabilities used for the design of part span shrouds and to gain a better understanding of the dynamic behavior of shrouded assemblies, a jointed experimental and numerical approach has been conducted. A first experimental test based on a cantilever beam is considered. The beam, excited by a controlled electrodynamic shaker, is associated to a dry friction damper at its free end. A numerical finite element analysis and a macroslip model of contact has been developed. The solution method in time domain allows accurate computations of response levels and gives the main harmonics of the steady state response. Comparison between numerical and experimental results is very good. A second experimental set up is constituted by an assembly of 13 beams, cyclically mounted around a common disk and linked by geometrically simplified shrouds. The set up allows controlling the resultant forces in the contact and is able to exhibit all states of contact from fully slipping to fully stuck. The first results obtained are associated to a single couple of blades brought into contact.