Research On Nonlinear Dynamic Characteristics Of Rotor-Bearing System In Maneuvering Flight

The maneuvering flight of aircraft refers to the flight action which flight status of an aircraft is changing.It is one of the important indexes to evaluate the performance of the military aircraft.In recent years,accidental crashes often occur,which are generally caused by engine diagnosis.The system fault prototype can be attributed to the vibration of the rotor system.So it is very necessary to study the nonlinear dynamic characteristics of the rotor system in the maneuver flight.This paper studied a single rotor system and a dual-rotor system which has the intermediary bearing.The main research contents are briefly summarized as follows:(1)A simple bias rotor system is used as the model,and the dynamic differential equations of the system are derived from the Lagrange equation.Then the equations are sorted to obtain the dynamic loads of the system under different maneuver flight.The double disc rotor coith rolling bearing model is build and the motion functions of this system were derived by finite element method.The obtained maneuvering load was applied to this model.In the end,the solving method of large-scale complex finite element rotor system-Newmark beta method is introduced,which provided theoretical basis for dynamic simulation of the whole paper.(2)The nonlinear dynamic behavior of a double disk rotor rolling bearing system in horizontal hover,climb-dive and roll maneuver is studied,and the influences of maneuver load and eccentricity to the nonlinear dynamics of the rotor system under different flight conditions are analyzed.The results show that horizontal circling and climbing-diving maneuver load can cause the center of the rotor to be offset.The increase of maneuver load can improve the stability of the system.Under the rolling action,the center of the rotor shaft center does not shift,but the size of the rotor shaft orbits varies with the change of the roll angular velocity.(3)A dynamic model of the rotor bearing system with the new rub impact is established.The numerical method is used to calculate the responses of system in the horizontal circling and the influences of the maneuver load,bearing clearance,impact stiffness coefficient,leaf number,eccentricity and squeeze film damper to the system nonlinear dynamics.The results show that the system generates a phenomenon of sub harmonic resonance,resulting the amplitude of vibration response of the system increasing.With the increase of the maneuver load,the system al?ays has the complex nonlinear phenomenon.The increase of bearing gap causes the system to produce complex nonlinear phenomena.With the increase of impact stiffness coefficient,the system produces a large number of dividing frequency and double frequency components,which can be used as the characteristic frequency of rub impact fault.With the increase of leaf number,the rub impact force increases,so as to make the system produces complex nonlinear phenomena.The vibration amplitude increases with the increase of the eccentricity of the system.The stability of SFD system has a great improvement in the global rotational speed,and has a good effect of vibration reduction.At the critical speed,the damping effect is the best.(4)A dynamic model of the SFD-rolling bearing dual-rotor system is established.The results show that maneuver load has little effect on the beat vibration.Compared co-rotating with reverse rotation,the orbits of system are very different.The smaller the intermediate bearing,the better the stability of the system.The increase of maneuver load can reduce the nonlinear vibration of the dual-rotor system with rub impact.The system causes complex nonlinear vibration when the internal and external rotor speed ratio is equal to 1.1.