Identification of Computational Models of the Dynamics of Gas Turbine Unit Rotors with Magnetic Bearings by Incomplete Data for Design Automation

Abstract

The paper discusses simulation of the rotor dynamics phenomena in a power gas turbine unit (GTU) on the basis of numerical approaches and presents the results of a finite element analysis of the GTU rotor dynamics with identification of computational models based on incomplete data. They include parametric modeling and identification of the design finite element model of the rotor of a gas turbine unit in active magnetic bearings (AMBs) in terms of geometric and dynamic parameters. The parametric models of the gas turbine engine and generator rotors are created using beam finite elements. Depending on the section of the shaft line, the final element was assigned either with circular or annular cross-sections. Finite elements of an elastic connection were used for AMB modeling. The search for the geometric and physical parameters for the GTU rotor model was carried out in two stages – varying the geometric parameters and selecting the reduced properties of materials for individual sections. The criterion for the adequacy and suitability of the computational model for the further execution of various dynamic analyzes was the satisfaction of the known data (the values of natural frequencies and critical speeds, the amplitude-frequency characteristics of the entire GTU shaft line and isolated rotors). The results of the analysis of forced vibrations allowed verifying the models by the values of the resonance mode frequencies according to the data known from the open literature at the given parameters of imbalance and damping. Models are further suitable for computer-aided design using information technology.