Nonsynchronous vibrations of turbomachinery bladed discs

The paper brings forward the method of determining nonsynchronous vibrations of turbomachinery bladed discs, based on the hypothesis of mechanical generator. Turbomachinery stages represented as a mechanical generator open up new opportunities for test results interpretation for the purpose of gas-turbine engine mounts development and make it possible to improve the reliability of diagnostics of nonsynchronous vibrations and their occurrence and development mechanism. Turbomachinery bladed discs represented as a mechanical generator component part revealed that nonsynchronous vibrations of turbomachinery bladed disc are determined by design features of bladed disc and vane. The paper contains some examples of spectra for fan strain-gauging results, on the basis of which the analysis of nonsynchronous vibrations of turbomachinery bladed discs was carried out. Vibrations of bladed disc with forward and backward strain waves having coefficients k1 and k2, respectively, are considered as a mode of bladed disc being a part of the mechanical generator, which vibration mode is presented by the algebraic sum of broken coefficients. The algebraic sum of these coefficients equals with a ratio of vibration frequency of bladed disc as a mechanical generator part to rotation frequency. The introduced generator of mechanical vibrations model can be applied to the analysis of nonsynchronous vibrations when processing results of turbomachinery bladed discs rig tests.