Abstract
The centrifugal stress, thermal stress, and aerodynamic stress on the aero-engine rotating disk vary drastically with the change of the aero-engine operational state, greatly susceptible to inducing disk fatigue cracks. Especially in the twin-spool rotor system, due to the effect of the disk fatigue cracks, the vibration of the inner and outer rotors increases dramatically, and the rubbing phenomenon may even occur at the inter-shaft sealing position. The aim of this paper is to investigate the inter-shaft rubbing characteristics of a twin-spool rotor system with cracked disk. Firstly, the effect of disk’s crack is modeled by an equivalent unbalanced force, and the inter-shaft rubbing force between the inner and outer rotors is further derived using Hertz contact and Coulomb friction theories, based on which, the dynamic model for a twin-spool rotor system with disk’s crack and inter-shaft rubbing faults is developed by means of finite element method. Subsequently, using three-dimensional spectrum, rotating orbits, and Poincaré diagram, a comparison of inter-shaft rubbing behaviors of a twin-spool rotor system with and without crack is performed, and the effects of crack-related parameters such as crack width and depth on the inter-shaft rubbing characteristics of the twin-spool rotor system are discussed in depth. The results reveal that the appearance of the crack may cause the rotor system to evolve from partial inter-shaft rubbing state to full annular inter-shaft rubbing state. The growth of crack width leads to a drastic increase in the unbalance of the cracked disk, which in turn results in a rise in the vibration amplitude of the rotor system. Besides, as the crack depth grows up, the rotor system may evolve from no rubbing state to partial inter-shaft rubbing state, and then from partial to full annular inter-shaft rubbing state. These findings can help to understand the inter-shaft rubbing characteristics of the twin-spool rotor system.
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