Research On Dynamical Characteristics Of Counter-rotating Dual-rotor Systems Of Aero-engines

The counter-rotating dual-rotor system has been widely applied in aero-enginefield, and it can decrease the influence of the gyroscopic moments created by the highpressure rotor and the low pressure rotor, reduce the torque of cases, and improve theflexibility of airplanes. Maneuvering flight is a significant characteristic ofaero-engines. The counter-rotating dual-rotor system of aero-engine is the subjectstudied, the dynamic characteristics of the system under fixed base and maneuveringconditions is analyzed through numerical calculation and experiments. The maincontents of this paper are as follows:(1) The current research of rotor dynamics under fixed base and maneuvering isreviewed, the theoretical basis of rotor dynamics and testing technology areintroduced.(2) For the counter-rotating dual-rotor system of aero-engine, the dynamicalmodel of the counter-rotating dual-rotor which considered the nonlinear influence ofthe inter-shaft bearing and the elastic support is presented with Lagrange equation, theinfluences of the amount of unbalance and the nonlinear stiffness coefficient of elasticsupport to the system response characteristics are studied. The conclusion indicatesthat, with the decrease of the amount of unbalance, the critical speed is reduced andthe amplitude is decreased, the jumping phenomenon of the outer rotor is disappeared,but the inner rotor’s is sustained. Under the influence of nonlinear stiffness, the outerrotor amplitude-frequency curve shows the hard characteristics, for the inner rotor, thedeviation will appear only when the nonlinear stiffness coefficient become a certainlarge formant. While the nonlinear stiffness coefficient decreased, the critical speed isreduced and the amplitude is increased. The the nonlinear response is studied byexperiment, the law of the change of the nonlinear response when one rotor rotatedunder constant speed and the other one rotated under increased speed is analyzed andcompared with the numerical analysis result to validate the veracity of the dynamicalmodel.(3) The maneuvering experiment of the counter-rotating dual-rotor system ismanufactured by our own experiment rig. The relations between the rotor dynamicsand the base movements are summarized and the ultraharmonic resonance undermaneuvering is studied. The conclusion indicates that, at the moment of maneuvering, the axis of the rotor will offset and the amplitude will increased, the maneuvering willhave an effect on the vibration of both fundamental and doubling frequency of therotor, the amplitude of the fundamental is increased, on the contrary, the doublingfrequency’s is decreased and it has larger variations.The research to the dynamical characteristic of the counter-rotating dual-rotorsystem is studied by theoretical analysis and experiment, the conclusion drawn fromtheory analysis and experiment has a significant value on the theory and practicalapplication of the aero-engine rotor systems.