Diagnosis Methodology of Joint Faults in Single-Stage Actuation Ring-Vanes System Based on FRF Characterization

The variable stator vanes (VSV) is prone to happen joint faults such as wear and stagnation due to complex structure and a large number of kinematic pairs. Based on the circumferential spatial distribution characteristics of the joints around actuation ring, this paper establishes a single-stage ring torsional inertia-spring model that considers nonlinearity caused by joint faults. Refer to a real aero-engine’s VSV structure, the system parameters of the model are obtained by simplifying, and then the motion differential equation of the system is obtained. The torsional vibration response of each vane of the system is obtained by the newmark$-\beta$ integral method. This paper also developed a diagnosis methodology based on the nonlinear output frequency response functions (NOFRFs), and established a second-order optimal weighted contribution rate indices Rm. Based on the torsional vibration response of each vane, the corresponding Rm is extracted. The asymmetry characteristic of the Rm around the single-stage actuation ring with fault to the excitation vane is established, and the influence of the excitation intensity and other factors on the asymmetry are analyzed. The results show that the diagnosis methodology proposed in this paper can effectively detect joint faults of VSV in aero-engine.