Time-varying vibration analysis based engine condition monitoring and diagnosis

Impact excitations, time-varying transfer routes and non-stationary response are typical characteristics of the reciprocating engine vibration. These characteristics make the engine vibration analysis more difficult than the rotating machinery. Focused on this problem, this paper details a thorough investigation from theoretical analysis to practical diagnosing approach design. Firstly, the inner-engine impacts are reasonably classified. Based on this, an analytical non-stationary vibration model is developed and discussed in details, on its time domain and time-frequency domain characteristics. Directed by these discussions, an applicable diagnosing approach is designed, which includes the software-based synchronization for non-stationary signal pretreatment, wavelet packet based filtering for impact signature extraction, as well as the Auto-Regressive model based Pseudo Wigner-Ville Distribution for integrated time-frequency signature extraction. These methodologies are successfully used in the practical diagnosis of the 6190ZLC diesel engine.