Analysis of the fault response transmission characteristics of the whole engine considering different supporting frame configurations

The fault vibration information in the rotor is transmitted to the external environment through structures such as bearings, bearing housings, and supporting frames. A thorough study of the transmission laws of rotor fault vibration information is of great significance for fault diagnosis in aero-engines. In this study, a rotor-bearing-supporting frame-casing whole engine system dynamic model was established using the lumped parameter method, incorporating both sheet-type and tie-bar supporting structures. The system’s outer casing vibration response under unbalance, misalignment, and bearing fault excitations was solved using the Newmark-β method. Simulated fault experiments were conducted on a whole engine vibration transmission test bench to investigate the transmission characteristics of different fault vibration responses through different supporting frames, thus validating the accuracy of the proposed model and vibration evaluation method. The results show that, when passing through different supporting frame structures, both the rotor fundamental frequency amplitude and the fault characteristic frequency amplitude experience attenuation. The smaller the vibration transmission index, the closer the path is to the fault excitation source. For the centrally mounted rotor system, unbalance and misalignment faults generate larger vibration amplitudes at the roller bearing end, and the tie-bar supporting structure results in higher vibration attenuation. When inner-ring and outer-ring bearing faults occur, the fundamental frequency amplitude of the system experiences the highest attenuation rate after passing through the tie-bar supporting structure, reaching 93.72% and 99.58%, respectively.