CONSTRAINT CHARACTERISTICS OF BEARING-SUPPORT SYSTEM WITH PEDESTAL LOOSENESS

In the bearing-support system of aero engine, there is often a fit clearance between bearing outer ring and pedestal, which is called pedestal looseness, causing potential influence on the dynamic response of rotor system. The essence of this influence is that the constraint characteristics of the bearing-support system changes as the rotor motion status changes. In this paper, a comprehensive model of pedestal looseness is proposed to accurately describe the interaction between the bearing and the pedestal. The concept of constraint characteristics is enriched, making it more accurate in describing the constraint effect of the bearing-support system on the rotor motion. A computational analysis is conducted on the constraint characteristics, and the influence of key parameters on them is investigated. The results show that the constraint stiffness decreases compared to bearing-support system without pedestal looseness when the dynamic support load is large. When the rotor is in non-synchronous whirling status, the harmonic/combination frequency components occur in dynamic response. Increasing the preload or reducing the fit clearance reduces the variation of the constraint stiffness with changes in load amplitude, and the amplitude of harmonic/combination frequency components is lowered, improving the robustness of constraint characteristics. This study provides theoretical methods for the design of bearing-support system and contributes to the reliability and safety design of aero engine.