Dynamic modeling of rotating machines (applications of numerical techniques)

Miscellaneous numerical techniques have been applied to the development of a discrete model for the analysis and dynamic simulation of rotating machines. The rotor inertia and stiffness matrices were derived with the Finite Element Method (FEM). Dynamic models for the supports were coupled to the initial rotor model, thus accounting for the influence of bearings, supporting structure and foundation on the global model. The resulting system of differential equations after coupling the supports' model was reduced using a modal synthesis method, allowing the expression of the reduced system in terms of physical coordinates instead of modal coordinates. This yields transient or steady state response calculations with considerable savings of computational effort, also allowing the use of experimentally measured modes and frequencies for a better fitting of the models to the physical systems. A reduced model was prepared to simulate the transient response of a simplified rotor previously studied by other authors. This provided a good way for verifying the model, the modal synthesis method and the numerical integration techniques. Some calculated and measured examples of the unbalance steady state response of an experimental rig are also included.