Study on the New Concept of the Rotors and Supporting Structure Transformation for Non-linear Vibrations Analysis

Study on the New Concept of the Rotors and Supporting Structure Transformation for Non-linear Vibrations Analysis

The problem of mathematical description of two basic sub-systems of a rotating machine, the line of rotors with bearings and the supporting structure, will be discussed in this paper. We must use non-linear analysis to solve the equations of motion in another reference system to obtain non-elliptic trajectories with different types of defects in system operation and complicated vibration spectra coded in their shapes – which forms the basis for technical diagnostics. The line of rotors with constructional and operational imperfections (misalignment, shaft cracks), and, of course, the slide bearings and labyrinth seals, are among the subsystems that often show non-linear characteristics. At the same time, the supporting structure can be viewed as a subsystem with linear characteristics with sufficient accuracy. A central issue in this situation is how to combine the supporting structure, which has linear characteristics, with the line of rotors and bearings, which rests on the supporting structure and clearly represents non-linear characteristics. Such an elegant notation for the entire machine in the form of a complex matrix is no longer feasible. The situation is getting significantly more complex from a statistical standpoint. This evaluation is based primarily on the construction’s properties, specifically the degree of complexity of its modal model, as well as available measurement or simulation data and potential interactions of supporting structure elements that may expose non-linear characteristics. We will propose solutions to this problem in the form of so-called adequacy intervals of the supporting structure dynamic characteristics, with relevant transformations, and we will present a novel concept for incorporating those characteristics into the rotor line dynamics, based on so-called weight functions proportional to the vibration spectrum of the supporting structure. The proposed definition has the potential to be extremely useful in identifying defect-symptom relationships for use in model-based diagnostics, a new and rapidly evolving field of research.

Author (s) Details

Jan Kicinski
Institute of Fluid-Flow Machinery, Polish Academy of Sciences (IMP PAN), Fiszera 14, 80-231 Gdar´ısk, Poland.

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