Analysis of the similarity design and vibration transmission characteristics of typical support structures of an aero-engine

Abstract

In the vibration test of an entire aero-engine, the magnitude and phase of the unbalanced vector of the internal rotor must be identified based on the vibration signal of the measuring point on the casing. Therefore, in addition to understanding the vibration transmission law between the high- and low-pressure rotors under unbalanced excitation, the vibration transmission law of the support structure must be studied urgently. However, few studies have investigated the vibration transfer characteristics of typical support structures. In this study, the similarity design of typical support structures was first performed, and the structural parameters of the core member squirrel cage were determined using theoretical calculations. Subsequently, the bush and spring elements were used to establish the connection between the inner and outer rings of the bearing to realise the equivalent simulation of the bearing stiffness. Using this method, refined finite element models of elastic and rigid support structures were established, and the accuracy of the model was verified based on low-speed rotating vibration and hammering tests. Furthermore, the unbalanced vibration transmission law of typical support structures was studied, and the vertical vibration transmission law from an aero-engine bearing pedestal to the panel was established with the vibration transmission rate as the quantitative index. Finally, considering the vital role of the squirrel cage, the influence of the local stiffness degradation of the squirrel cage on the unbalanced vibration transmission of the elastic support structure was studied. The research methods and results of this study can provide a basis for aero-engine assembly as well as manufacturing and structural performance evaluation.