Abstract
This paper focuses on the nonlinear response characteristics of an aero-engine dual-rotor-bearing system with flexible coupling misalignment faults in the low-pressure rotor system (rotor 2). The motion equations of the system are formulated by using finite element method, in which the excitations induced by the misalignment faults, the dual-unbalance excitations of the two rotors (the high-pressure rotor system-rotor 1 and the low-pressure rotor system-rotor 2), the gravities, and the nonlinear force induced by the inter-shaft bearing are all considered. By using numerical calculation method, the motion equations are solved to obtain the nonlinear responses of the system. Then, the nonlinear responses for the alignment dual-rotor-bearing system are analyzed, the hardening type hysteresis characteristics with jump phenomenon are shown. Accordingly, the nonlinear responses affected by the amount of parallel misalignment and angular misalignment are discussed in detail. The results show that, with the increase of by the amount of parallel misalignment (angular misalignment), the frequency components 2 times rotational speed of rotor 2 appear, and the amplitudes of the responses at the super-harmonic frequency components and combined frequency components get larger for not only rotor 2 but also rotor 1, which indicates that the vibration characteristics of misalignment faults in rotor 2 can be transmitted to the rotor 1 and can be used to diagnose the misalignment faults. The results obtained in this paper will contribute to the response analysis for the aero-engine dual-rotor-bearing system with flexible coupling misalignment faults.
Highlights
Flexible coupling is widely used in rotary machinery systems such as aero-engines and gas turbines
The results obtained show that with the increase of Δy ( Δα ), besides the responses at the super-harmonic frequency component 2Ω2 get larger discussed in Ref. [23], the responses at the combined frequency components 2Ω1-Ω2, 2Ω2+Ω1 etc. increase for rotor 2 and rotor 1, which indicates that the vibration characteristics of misalignment faults in rotor 2 can be transmitted to the rotor 1
With the increase of the amount of parallel misalignment Δy (Δα), the super-harmonic frequency component 2Ω representing the misalignment signal increases for both rotor 2 and rotor 1, and the responses at the combined frequency components 2Ω − Ω, 2Ω + Ω etc. get larger, which indicates that the vibration characteristics of misalignment faults in rotor 2 can be transmitted to the rotor 1
Summary
Flexible coupling is widely used in rotary machinery systems such as aero-engines and gas turbines. DYNAMIC RESPONSE ANALYSIS FOR THE AERO-ENGINE DUAL-ROTOR-BEARING SYSTEM WITH FLEXIBLE COUPLING MISALIGNMENT FAULTS. Ma and Wang [11] systematically investigated oil-film instability laws of an overhung rotor system with parallel and angular misalignments, where the excitation forces/moments caused by coupling misalignment were relevant to one to four times shaft rotation speed. Influence of misalignment and its type on the forcing characteristics of flexible coupling has been discussed by experimentally investigating the vibration response of misaligned coupled rotors supported on rolling element bearings [13], the results shows that the 2X harmonic vibration response is still the most widely reported misalignment signature but not sufficient, and the presence and type of misalignment (parallel and angular misalignment) have significant influence on harmonic content of the misalignment excitation forces. An aero-engine dual-rotor-bearing system with flexible coupling misalignment faults is built and studied, wherein the dual-unbalance, misalignment forces in the low-pressure rotor, and the nonlinearity of the inter-shaft bearing are fully considered. The results obtained show that with the increase of Δy ( Δα ), besides the responses at the super-harmonic frequency component 2Ω2 get larger discussed in Ref. [23], the responses at the combined frequency components 2Ω1-Ω2, 2Ω2+Ω1 etc. increase for rotor 2 and rotor 1, which indicates that the vibration characteristics of misalignment faults in rotor 2 can be transmitted to the rotor 1
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