Modal analysis of the coupled vibration in an aero-turbine compressor blisk considering both aerodynamic and centrifugal load

Abstract

To lighten the aircraft engine and improve its propulsion efficiency, many aero engines adopt the blisk structure comprising both the rotor disk and blades. Since the disk becomes thinner, the stiffness of the structure decreased apparently, which causes the occurrence of large amplitude vibration in the blisk. This passage utilizes the finite element analysis (FEA) and computational fluid dynamics (CFD) simulation software to investigate the coupled vibration characteristics between the blades and the disk of the blisk with realistic geometric data, in which the aerodynamic load and centrifugal load are considered. At first, the CFD and finite element models of an aero-turbine compressor blisk are built. Then the pressure load data under some critical rotating speeds from CFD simulation are communicated to FEA software by data interpolating method, and the simulation of modal characteristics of the blisk is conducted in FEA. At last, the natural modal characteristics of the blisk structure are obtained, including the resonance speed Campbell diagram, the natural frequencies and corresponding mode shapes. According to the Campbell diagram, it indicates that the most critical mode is the fourth order mode. It is found that the mode shape of the fourth order in the blisk is the coupling of the disk torsional and blades first bending vibration. It is easy to lead to vibration failure when large amplitude vibration of the fourth mode occurs in the blisk. Also, it could also conclude that the modal characteristics of the coupled vibration in the rotating blisk are very sensitive to the disk stiffness. These results provide basic data for the further research in nonlinear vibration and structure optimization of the blisk, and also a simulating method to investigate coupled vibration between the blades and the disk of the blisk considering both aerodynamic and centrifugal load.