Abstract
This paper aims to classify bifurcation modes for two interrelated primary resonances of a simple dual-rotor system under double frequency excitations. The four degree-of-freedom (4DOF) dynamic equations of the system considering the nonlinearity of the intershaft bearing can be obtained by using the assumed mode method (AMM) and Lagrange’s equation. A simplified method for dynamic equations is developed due to the symmetry of rotors, based on which the amplitude frequency equations for two interrelated primary resonances are obtained by using the multiple scales method. Furthermore, the validity of the simplified method for dynamic equations and the amplitude frequency equations solved by the multiple scales method are confirmed by numerical verification. Afterwards, the bifurcation analysis for two interrelated primary resonances is carried out according to the two-state-variable singularity method. There exist a total of three different types of bifurcation modes because of double frequency excitations of the dual-rotor system and the nonlinearity of the intershaft bearing. The second primary resonance is more prone to have nonlinear dynamic characteristics than the first primary resonance. This discovery indicates that two interrelated primary resonances of the dual-rotor system may have different bifurcation modes under the same dynamic parameters.
Highlights
With the development of aero-engines towards higher thrust-weight ratio and better aerodynamic stability [1], the dual-rotor structure has been widely used in the field of aero-engines
Different from Gupta et al [7], a dual-rotor test rig composed of two coaxial shafts was developed by Guskov et al [9], where two shafts are linked by an intershaft bearing and rotate individually
Zhang et al [10, 11] successively put forward the whole-beat correlation method and the nonwhole beat correlation method to identify unbalance responses of a dual-rotor system with a slight rotation speed difference
Summary
With the development of aero-engines towards higher thrust-weight ratio and better aerodynamic stability [1], the dual-rotor structure has been widely used in the field of aero-engines. Sun et al [15, 16] investigated the nonlinear dynamical behaviors of a dual-rotor aero-engine with rub impact by means of an analytic method, namely, MHB-AFT (multiharmonic balance-alternating frequency/time domain). Is research applied the two-state-variable singularity method to investigate bifurcation modes for the nonlinear dual-rotor system. E purpose of this paper is to investigate bifurcation modes for two interrelated primary resonances of a dual-rotor system based on the two-state-variable singularity method, where the double frequency excitations of the dual-rotor system and the nonlinearity of the intershaft bearing are taken into consideration. The bifurcation analysis for two interrelated primary resonances of the dual-rotor system could be carried out based on the twostate-variable singularity method It shows the second primary resonance is more prone to have nonlinear dynamic characteristics than the first primary resonance
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