Dynamic characteristics of co-rotating/counter-rotating dual-rotor system

A dynamic model of dual-rotor was set up. The influence of inter-shaft bearing stiffness and the gyroscopic moments of high and low pressure rotors were considered in this model. The difference of co-rotating or counter-rotating dual-rotor's critical speed characteristics and unbalance response and the influence of speed ratio on co-rotating or counter-rotating dual-rotor's critical speed characteristics and unbalance response were revealed by numerical analysis and experiments. The results show that, gyroscopic moment is a main influential factor to the rotor stiffness of dual-rotor system with inter-shaft bearing, and the changes of stiffness are related to the speed ratio and the relative rotating direction of inner and outer rotors, further causing the change of co-rotating or counter-rotating dual-rotor's critical speed characteristics and unbalance response. Compared with the co-rotating dual-rotor of the same structure with the counter-rotating dual-rotor, the counter-rotating dual-rotor's unbalance response is more obvious than the co-rotating dual-rotor's under the same unbalance mass, and for this reason the unbalance mass of counter-rotating dual-rotor's inner and outer rotors should be controlled more strictly during the dynamic balance.