Experimental Study on Dynamic Design Method of Dual-Rotor System with Inter-Shaft Bearing

Currently, the primary configuration adopted by aero-engine is dual-rotor system with inter-shaft bearing. This configuration, as a multisource excitation system, has prominent vibration problems. In order to overcome this problem, the current rotor dynamics design method has gradually transitioned from the traditional critical speed safety margin design method to the emerging acceptability mode design method, but the advantages and disadvantages of the two are still unknown. Therefore, according to different design methods, a double rotor tester with inter-shaft bearing is established, and the vibration response test is carried out under different design conditions. The results show that the dual-rotor system designed with the acceptability mode method can stably operate for no less than 3600 seconds at critical speed under an imbalance exceeding the design value by 178%. After the tester was removed from the design condition, the damping ratio provided by the damper decreased by 56.5 per cent and the amount of tolerated fluctuation in the low-pressure rotor decreased by 47.1 per cent due to the first nodal point design parameter change. However, when the dual-rotor tester designed according to the acceptability mode design method crosses the critical speed quickly, the peak value of each modal vibration is reduced by at least 17.3 %. Thus, the acceptability mode design method possesses greater reliability. But, for engines that follow the better design method and do not frequently operate at critical speeds, the vibration reduction measure of greatest efficiency remains to be rapidly crossing the critical speed.