Dynamical Structural Modification for Rotordynamic Application

Abstract

In the field of rotordynamics, the critical speeds of a rotating system have a wide range of implications throughout industry as the operating speeds for current machine design are pushed to the limit. Moreover, interaction or coupling of a rotordynamic system with the base and/or auxiliary structures influences the dynamic behavior as well as the critical speeds for the coupled system. In order to ensure that the critical speeds of the coupled system is not excited, structural modification of primary structures (e.g. rotordynamic, foundation, auxiliary units etc.) and/or of the coupling parameters may be necessary by passive or active means. The modeling of these coupled systems, as well as the coupling mechanism, may lead to approximation errors. These errors may deteriorate the desired dynamic response of the coupled system. In order to avoid such modeling errors, this paper investigates structural modification and control strategies that are purely based on the transfer functions of the individual subsystems of the overall coupled system. The proposed concept is demonstrated by numerical examples, in which the receptance transfer functions are used to guide structural modifications; for example, to change the critical speed of a coupled rotordynamic system to a desired value. Coupling of turbine-generator assembly and rotordynamic system with flexible base is considered here.