Abstract
To make up deficiency of the finite element method in predicting nonlinear dynamic characteristics of coaxial rotor systems, nonlinear dynamic model of a coaxial rotor system was established with a method combining the finite element method and the fixed interface modal synthesis method. Then an implicit time domain method was presented to solve the nonlinear equations of motion thus dynamic characteristics of the rotor system can be obtained. The computational efficiency of this method largely depends on the number of degrees of freedom with nonlinear forces acting on. With nonlinear forces of squeeze film damper and intermediate bearing considered, nonlinear dynamic response characteristics of the coaxial rotor system under multiple unbalance forces were studied in this work. The results showed that the unbalance excitation frequencies are dominant in the responses of the rotor system. Besides, due to coupling effect of the intermediate bearing some combinations of the unbalance excitation frequencies were also observed in the spectrogram. Stability and periodicity of the rotor system was investigated with bifurcation diagram, Poincare map and phase diagram. It was found that the rotor system executes multiple periods orbital motion under relatively low rotational speeds. With the increasing of rotational speed, the rotor system would execute quasi-periodic motion, chaotic motion and periodic motion again. The quasi-periodic motion and chaotic motion are closely related with the SFD. Finally, under relatively low speed, the nonlinear model was validated by comparing the simulation results with the experimental data. The proposed modeling and solving method is expected to provide theoretical and engineering basis for improving prediction of nonlinear dynamic characteristics of complex rotor systems.
Highlights
Rotor system is the main source of vibration of aeroengines
Nonlinear model of the rotor system is established with finite element method and fixed interface modal synthesis method; subsequently an implicit time-domain method based on Newmark- method is applied to solve the equations of motion of the reduced system dynamic characteristics can be obtained
A modeling method combining the finite element method and the fixed interface modal synthesis method has been developed in the work to establish the nonlinear model of a counter-rotating dual-rotor test rig for steady state nonlinear response analysis
Summary
Rotor system is the main source of vibration of aeroengines. Stability and reliability of aeroengines mostly depend on dynamic behaviors of the rotor system. All these problem solving measures are based on accurate approximation of the actual rotor system. Nonlinear model of a counter-rotating coaxial test rig is established with a method combining the finite element method and the component modal synthesis method for accuracy and efficiency. Nonlinear forces exerted by the squeeze film damper and the intermediate bearing were considered With this nonlinear model and the improved Newmark- method, dynamic characteristics of the rotor system was obtained and further analysis was made and compared with the experimental results
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
