Abstract: The finite element model of multi-span rubbing rotor system has a large number of degrees of freedom，which affects the efficiency of the numerical simulation seriously. To overcome this problem and remain the accuracy of numerical simulation at the same time， a new dimension-reduced incremental harmonic balance method combining the fixed interface component mode synthesis method was presented. Firstly， the degree of freedom was reduced by the fixed interface component mode synthesis method， and then the incremental harmonic balance method was applied to obtain the stable state response of the dimension-reduced system， and at last the response of the original rotor system can be obtained. The method can not only get the stable state solution directly， but also be combined with the arc-length method to obtain the unstable state response. The results show that a two-span rotor system can reach good accuracy and high efficiency with few dominant modes.

Key words: rotor system, rubbing, fixed interface component mode synthesis method, incremental harmonic balance method, arc-length method