Study On Nonlinear Vibration Behaviors Of Aero-engine Eccentric Dual-rotor System

Aero-engine is known as "the heart of the aircraft", the performance of aero-engine directly related to aircraft flight safety, and rotor system is the local oscillator of the aero-engine. The structure of an aero-engine is very complex, the working rotation speed of the rotor system is high, to ensure its working security, it’s necessary to analyze the dynamic characteristics of the rotor system. The analysis in this paper use finite element method and ANSYS rotor dynamics analysis module.First, establish the mathematical mode of the dual rotor system, in the establishing process, the influence of the asymmetric support of the high and low rotor, mass eccentricity and gyroscopic effect are fully taken into account. Establish the differential equation of the high and low rotor system using non-conservative Lagrange equation. The support system positioned to support and location the rotor, its stiffness has a direct impact on dynamic characteristics of the rotor system. The aero-engine using three elastic supports to adjust the critical speed of the rotor system, calculating the supports’stiffness is necessary. In this paper, analyze the elastic supports’static stiffness and the composite stiffness with bearings using finite element method. Sample the dual-rotor system reasonably according to the actual situation, establishing its three-dimensional mode and analyzing its natural frequency and critical speed, which consider gyroscopic torque with the change of speed. Do steady-state harmonic response analysis with unbalance mass rotor system. Research the impact of position of the unbalanced mass to the amplitude of the supports. Through transient analysis of rotor startup process, compare the amplitude of supports in different accelerations and unbalance mass conditions. Analysis how the amplitude of each support attenuate when encounter of sudden unbalanced external force.The margin of the critical speed and the operating rated speed of the dual-rotor system is greater than20%, it means the design of the critical speed is rationale. In the analysis of steady-state harmonic response, start-up transient analysis, sudden unbalanced external force transient analysis, the results are consistent with the inspection literature, this proves the correctness of the analysis.