Methodology of Vibroacoustic Monitoring and Diagnosis of Initial Damage of Elements of Rotating Systems

The chapter provides materials for the and improvement of the vibroacoustic condition monitoring of complex rotating system during operation, such as, aviation gas-turbine engines (GTE). The low-frequency vibration and acoustic noise in the range 0–25 kHz is used as diagnostic information. Diagnostic model of GTE has been developed for the vibroacoustical diagnosis of the crack-like damages of blades at the steady-state and non-steady-state modes of GTE. On the bases of its the model of measured vibriacoustical signal is created as diagnostic information. The diagnostic information is characterized by complexity and variety, and the measured signals are the local or essential non-steady-state processes. The results of processing of such noise-like signals are often rather complex for interpreting, comparing and deciding on the technical condition of elements of the rotating system. We propose to use several stages or levels of processing of diagnostic information, based on various methods in order to detect the faults features and increase their diagnostic value. The following signal processing are proposed for application: Time-frequency analysis, High-order spectral analysis, Wavelet decomposition, Dimensionless characteristics of vibroacoustical signals and Fractal analysis. Signal processing was performed using simulated vibroacoustical signals at the steady-state and non-steady-state modes of GTE in order to diagnose the initial crack-like damage of the blade. And two-level signal processing was performed using measured signals during the physical simulation of the turbine imitator. For the vibroacoustic diagnosis the crack-like damage of the rotor’s shaft, the simulated signal was processed at the rotor acceleration mode. Multi-level signal processing was used to diagnose violations of the normal operating modes of the GTE using the example of diagnostics of the impact of foreign objects. The diagnostically features of crack-like damages of the rotating elements and violations of the normal operating modes of the GTE are proposed and investigated. On the basis of the research results a new multi-level system can be developed for multi-class diagnostics of GTE in steady-state and non-steady-state modes of operation.