This paper focuses on the research of the rubbing simulation method and dynamic characteristics of complex engine blades. Considering the influence of local blade contact and rotor whirl, a three-dimensional rubbing load and blade inertial load model is established through the spatial motion relationship. The above load model is assembled with the reduced-dimensional finite element model of the blade to obtain the rubbing dynamic equation. Combined with numerical solution techniques, a rubbing simulation method for complex engine blades is ultimately proposed. The proposed method is applied to conduct a rubbing analysis of the compressor blades of a certain aeroengine. The results show that tip rubbing can excite two rubbing states, which are related to the rubbing position. During the leading edge of the blade tip rubbing, the intermittent rubbing of the blade is easily to be excited. At this time, the blade repeatedly contacts and separates from the casing, and the blade exhibits high-frequency and high-amplitude modal vibration at 8 000 Hz. During the trailing edge of the blade tip rubbing, the full circumferential rubbing is more likely to be excited, and the blade undergoes static deformation at this time. The non-synchronous whirl of the rotor significantly increases the nonlinearity of the blade rubbing behavior. The vibration frequency of the blade will have complex combined frequencies related to the whirl frequencies f_e and f_n. Reducing the rubbing stiffness and friction coefficient can effectively suppress the overall vibration of the blade under tip rubbing. This paper can provide necessary theoretical method support for the dynamic analysis of aero-engine blades and clearance design.

This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with rub-impact in aero-engine. The finite solid element method combined with a constraint stiffness model produced by rub-impact is introduced to build the governing equation of the complicated nonlinear dual-rotor system. In order to deal with the efficiency and numerical divergence in the process of solving the nonlinear modes of this large-scale nonlinear system, an analysis strategy is proposed by integrating a two-layer reduction technique into the harmonic balance method. The effectiveness of the analysis strategy is validated by applying to a simple rotor system, which can easily obtain the theoretical result. Based on the modeling method and analysis strategy, the modal characteristics of an aero-engine dual-rotor system with rub-impact are revealed. The results show that the modal frequency of the dual-rotor system increases when rub-impact occurs and has the feature of interval, which allows us to obtain the critical speeds of the rubbing system by traditional Campbell diagram. The rotation direction is an important factor since it can not only affect the gyroscopic effect but also change the friction effect of the rub-impact. It is found that the modal frequencies of the counter-rotation dual-rotor are less than those of co-rotation condition. More importantly, the forward modes of the counter-rotation dual-rotor may be instable when rub-impact occurs at a certain rotor, while the corresponding modes under the co-rotation condition are always stable. Furthermore, by analyzing the rubbing response of the dual-rotor, it is found that the modal characteristics have an important influence on rotor’s response. The instable forward modes existing in the counter-rotation dual-rotor may lead to the divergence of the response when passing the corresponding critical speed.