Alford力和中介轴承对双转子系统动力学特性的影响

Effects of the Alford force and inter-shaft bearing on the dynamic characteristics of a dual-rotor system

以航空发动机典型双转子-中介轴承系统为研究对象,综合考虑发动机工作时气流激励力的影响和双转子中介轴承特性,研究了包含气流激励Alford力和中介轴承非线性力的双转子系统的动力学特性。采用Euler-Bernoulli梁理论建立了系统的动力学模型,在模型中引入非线性中介轴承力与Alford力,利用有限单元法和Newmark-β法求解了系统的动力学响应。计算结果显示,Alford力以组合频率和连续频率的形式影响系统运动,而且极易激起中介轴承力的非线性特性。Alford力会使系统的临界转速变大。随着转速的增加,中介轴承力对转子系统的影响逐渐减小,而Alford力的影响则逐渐增加。此外,中介轴承游隙的变化与Alford力的特性深度耦合,不同的游隙下轴承力与Alford力共同引起系统的周期、拟周期和混沌等不同的运动状态。

Taking the typical dual-rotor-inter-shaft bearing system of an aero-engine as the research object, the influences of the airflow excitation force and the characteristics of dual-rotor inter-shaft bearing, were comprehensively considered and the dynamic characteristics of the dual-rotor system under the airflow excitation Alford force and the nonlinear inter-shaft bearing force were studied. The dynamic model of the system was established by using the Euler-Bernoulli beam theory, and the nonlinear intermediate bearing force and Alford force were introduced into the model. The finite element method and Newmark-β method were used to solve the dynamic responses of the system. The calculation results show that the Alford force affects the motion of the system to produce combined frequency and continuous frequency components, and it is easy to excite the nonlinear characteristics of the intermediate bearing force. The Alford force increases the critical speed of the system.With the increase of rotational speed, the influence of intermediate bearing force on the rotor system decreases, while the influence of Alford force increases. In addition, the change of the clearance of the intermediate bearing is deeply coupled with the characteristics of the Alford force. Under different bearing clearances, the bearing force and the Alford force jointly cause different motion states such as period, quasi-period and chaos states of the system.