Abstract
After the blade losing, the aero-engine rotor system is subjected to multiple loads, including sudden unbalance excitation, angular acceleration excitation caused by time-varying speed, and rub-impact excitation due to the fan blade off (FBO), which results in a complex dynamic characteristic of the rotor system. At present, the dynamic response mechanism analysis and high-precision simulation results in this case are not complete, which seriously restricts the safety design and verification in the engine development process. This paper analyzes the load characteristics of the rotor when FBO occurs. Then the dynamic equation of inertia asymmetric rotor is carried out considering the combined action of multiple loads. the dynamic response analysis model of the low-pressure rotor of the turbofan engine with the condition of blade loss is established, the dynamic response of inertia symmetric rotor and inertia asymmetric rotor are compared and studied. A safety design idea of the support structure is proposed according to the characteristics of the inertia asymmetric rotor structure. This research shows that after the FBO occurs, the vibration response of the rotor increases sharply when it decelerates passing the critical speed, and the rotor system appears backward whirl frequency with the action of multiple loads. Compared with the inertia symmetric rotor, the inertia asymmetric rotor is more prone to appear backward whirl characteristics. According to the characteristics of inertia asymmetric rotor load with multiple loads, this paper changes the dynamic characteristics of rotor system by reducing the support stiffness, and increases the support damping to improve the energy dissipation, so as to reduce the vibration response of the inertia asymmetric rotor and to ensure the integrity of the support structure after blade loss.